Communication apparatus and communication method for discrete-fourier-transforming a time domain symbol to a frequency domain signal and mapping the transformed signal on frequency bands

ABSTRACT

Provided is a radio communication device which can reduce ISI caused by destruction of an orthogonal DFT matrix even when an SC-FDMA signal is divided into a plurality of clusters and the clusters are respectively mapped to discontinuous frequency bands. The radio communication device includes a DFT unit ( 110 ), a division unit ( 111 ), and a mapping unit ( 112 ). The DFT unit ( 110 ) uses the DFT matrix to execute a DFT process on a symbol sequence in a time region to generate a signal (SC-FDMA signal) of the frequency region. The division unit ( 111 ) generates a plurality of clusters by dividing the SC-FDMA signal with a partially orthogonal bandwidth corresponding to the vector length of some of the column vectors constituting the DFT matrix used in the DFT unit ( 110 ) and orthogonally intersecting at least partially. The mapping unit ( 112 ) maps the clusters to discontinuous frequency bands.

BACKGROUND

1. Technical Field

The present invention relates to a radio communication apparatus and asignal division method.

2. Description of the Related Art

In 3GPP LTE (3rd Generation Partnership Project Long Term Evolution),active studies are underway on standardization of a mobile communicationstandard to realize low-delay and high-speed transmission.

To realize low-delay and high-speed transmission, OFDM (OrthogonalFrequency Division Multiplexing) is adopted as a downlink (DL) multipleaccess scheme and SC-FDMA (Single-Carrier Frequency Division MultipleAccess) using DFT (Discrete Fourier Transform) precoding is adopted asan uplink (UL) multiple access scheme.

SC-FDMA using DFT precoding uses a DFT matrix (precoding matrix or DFTsequence) represented by, for example, an N×N matrix. Here, N is thesize of DFT (the number of DFT points). Furthermore, in an N×N DFTmatrix, N (N×1) column vectors are orthogonal to each other in DFT sizeN. SC-FDMA using DFT precoding forms an SC-FDMA signal (spectrum) byspreading and code-multiplexing a symbol sequence using this DFT matrix.

Furthermore, standardization of LTE-Advanced (or IMT (InternationalMobile Telecommunication)-Advanced) to realize higher-speedcommunication than LTE has started. In LTE-Advanced, a radiocommunication base station apparatus (hereinafter referred to as “basestation”) and a radio communication terminal apparatus (hereinafterreferred to as “terminal”) which are communicable using a wideband of,for example, 40 MHz or higher are expected to be introduced to realizehigher-speed communication.

As for an LTE uplink, uplink frequency resource allocation is limited tosuch allocation that SC-FDMA signals are mapped to continuous frequencybands in a localized manner to maintain single-carrier characteristics(e.g. low PAPR (Peak-to-Average Power Ratio) characteristics) of atransmission signal for realizing high coverage.

However, when frequency resource allocation is limited as describedabove, vacancy is produced in uplink shared frequency resources (e.g.PUSCH (Physical Uplink Shared CHannel)) and the efficiency of the use offrequency resources becomes worse. Thus, as a prior art for improvingthe efficiency of the use of frequency resources, clustered SC-FDMA(C-SC-FDMA) is proposed which divides an SC-FDMA signal into a pluralityof clusters and maps the plurality of clusters to discontinuousfrequency resources (e.g. see non-patent literature 1).

In C-SC-FDMA of the above prior art, a terminal generates C-SC-FDMAsignals by dividing an SC-FDMA signal (spectrum) generated through DFTprocessing into a plurality of clusters. The terminal then maps theplurality of clusters to discontinuous frequency resources (subcarriersor resource blocks (RB)). On the other hand, a base station appliesfrequency domain equalization (FDE) processing to the received C-SC-FDMAsignals (plurality of clusters) and combines the plurality of clustersafter the equalization. The base station then applies IDFT (InverseDiscrete Fourier Transform) processing to the combined signal andthereby obtains a time domain signal.

C-SC-FDMA can allocate frequency resources among a plurality ofterminals more flexibly than SC-FDMA by mapping the plurality ofclusters to a plurality of discontinuous frequency resources, and canthereby improve the efficiency of the use of frequency resources andmultiuser diversity effect. Furthermore, C-SC-FDMA has a smaller PAPRthan that of OFDMA (Orthogonal Frequency Division Multiple Access), andcan thereby expand uplink coverage more than OFDMA.

Furthermore, a C-SC-FDMA configuration can be easily realized by onlyadding a component that divides an SC-FDMA signal (spectrum) into aplurality of clusters to the terminal and adding a component thatcombines a plurality of clusters to the base station in the conventionalSC-FDMA configuration.

CITATION LIST Non-Patent Literature

NPL 1

R1-081842, “LTE-A Requirements, Agenda Item 6.2: LTE-A Proposals forevolution,” 3GPP RAN WG1 #53, Kansas City, Mo., USA, May 5-9, 2008.

BRIEF SUMMARY Technical Problem

According to the above prior art, the base station divides an SC-FDMAsignal (spectrum) of each terminal with an arbitrary frequency accordingto a state of availability of uplink frequency resources and a conditionof the propagation path between a plurality of terminals and the basestation, allocates a plurality of clusters thereby generated to aplurality of uplink frequency resources respectively and reportsinformation showing the allocation result to the terminals. The terminaldivides the SC-FDMA signal (spectrum) which is the output of DFTprocessing with an arbitrary bandwidth, maps the plurality of clustersto a plurality of uplink frequency resources allocated by the basestation respectively and thereby generates C-SC-FDMA signals.

However, since a wide uplink radio frequency band (wideband radiochannel) is frequency selective, the frequency correlation betweenchannels through which a plurality of clusters mapped to differentdiscontinuous frequency bands propagate decreases. Thus, even when thebase station equalizes C-SC-FDMA signals (a plurality of clusters)through FDE processing, the equalization channel gain (that is,frequency channel gain after FDE weight multiplication) may considerablydiffer among the plurality of clusters. Therefore, the equalizationchannel gain may drastically change at a combining point (that is, thepoint of division at which the terminal divides the SC-FDMA signal) ofthe plurality of clusters. That is, a discontinuous point may occur in avariation (that is, envelope of reception spectrum) in the equalizationchannel gain at the combining point of the plurality of clusters.

Here, to keep minimal the loss of orthogonality of a DFT matrix in allfrequency bands (that is, the sum of frequency bands to which aplurality of clusters are mapped) to which C-SC-FDMA signals are mapped,the equalization channel gain in all frequency bands to which theplurality of clusters are mapped needs to be a slow variation. Thus,when a discontinuous point occurs in a variation of the equalizationchannel gain at a combining point of the plurality of clusters as in theabove described prior art, the orthogonality of the DFT matrix isconsiderably destroyed in the frequency band to which the C-SC-FDMAsignals are mapped. Therefore, the C-SC-FDMA signals are more impactedby inter-symbol interference (ISI) caused by the loss of orthogonalityof the DFT matrix. Especially when high-level M-ary modulation such as64 QAM whose Euclidian distance between signal points is very short isused, the C-SC-FDMA signals are more impacted by ISI, and thereforedeterioration of transmission characteristics is greater. Furthermore,as the number of clusters (the number of fractions of SC-FDMA signal)increases, the number of discontinuous points between clustersincreases, and therefore ISI caused by the loss of orthogonality of theDFT matrix further increases.

The present invention has been implemented in view of such problems andit is therefore an object of the present invention to provide a radiocommunication apparatus and a signal division method capable of reducingISI caused by the loss of orthogonality of a DFT matrix even when anSC-FDMA signal is divided into a plurality of clusters and the pluralityof clusters are mapped to discontinuous frequency bands respectively,that is, when C-SC-FDMA is used.

Solution to Problem

A radio communication apparatus of the present invention adopts aconfiguration including a conversion section that generates a frequencydomain signal by applying DFT processing to a symbol sequence using aDFT matrix, a division section that divides the signal with a partiallyorthogonal bandwidth corresponding to a partially orthogonal vectorlength of some of a plurality of column vectors constituting the DFTmatrix and generates a plurality of clusters and a mapping section thatmaps the plurality of clusters to a plurality of discontinuous frequencybands respectively.

A signal division method of the present invention divides a frequencydomain signal with a partially orthogonal bandwidth corresponding to apartially orthogonal vector length of some of a plurality of columnvectors constituting a DFT matrix used to convert a time domain symbolsequence to the frequency domain signal and generates a plurality ofclusters.

Advantageous Effects of Invention

When dividing an SC-FDMA signal into a plurality of clusters and mappingthe plurality of clusters to discontinuous frequency bands (when usingC-SC-FDMA), the present invention can reduce ISI caused by the loss oforthogonality of a DFT matrix.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of a terminal according to Embodiment 1 of thepresent invention;

FIG. 2 is a diagram showing DFT processing according to Embodiment 1 ofthe present invention;

FIG. 3 is a diagram showing an example of DFT matrix according toEmbodiment 1 of the present invention;

FIG. 4A is a diagram showing a partially orthogonal relationshipaccording to Embodiment 1 of the present invention (when |I|=1);

FIG. 4B is a diagram showing a partially orthogonal relationshipaccording to Embodiment 1 of the present invention (when |I|=2);

FIG. 4C is a diagram showing a partially orthogonal relationshipaccording to Embodiment 1 of the present invention (when |I|=3);

FIG. 5A is a diagram showing division processing and mapping processingaccording to Embodiment 1 of the present invention;

FIG. 5B is a diagram showing a signal after FDE according to Embodiment1 of the present invention;

FIG. 5C is a diagram showing a signal after combining according toEmbodiment 1 of the present invention;

FIG. 6 is a diagram showing an orthogonal relationship of column vectorsaccording to Embodiment 1 of the present invention;

FIG. 7 is a diagram showing an orthogonal relationship of column vectorsaccording to Embodiment 1 of the present invention;

FIG. 8 is a diagram showing frequency interleaving processing accordingto Embodiment 1 of the present invention;

FIG. 9 is a block diagram of a terminal according to Embodiment 2 of thepresent invention;

FIG. 10A is a diagram showing precoding processing according toEmbodiment 2 of the present invention;

FIG. 10B is a diagram showing precoding processing according toEmbodiment 2 of the present invention;

FIG. 11 is a diagram showing processing using FSTD according toEmbodiment 2 of the present invention;

FIG. 12 is a diagram showing processing using FSTD according toEmbodiment 3 of the present invention;

FIG. 13 is a diagram showing processing using FSTD according toEmbodiment 3 of the present invention;

FIG. 14 is a diagram showing a relationship between a multiplier and acluster size according to Embodiment 4 of the present invention;

FIG. 15 is a block diagram of a terminal according to Embodiment 5 ofthe present invention;

FIG. 16 is a block diagram of a base station according to Embodiment 5of the present invention;

FIG. 17A is a diagram showing shifting processing according toEmbodiment 5 of the present invention (when z=0);

FIG. 17B is a diagram showing shifting processing according toEmbodiment 5 of the present invention (when z=3);

FIG. 18A is a diagram showing DFT output according to Embodiment 5 ofthe present invention;

FIG. 18B is a diagram showing shifting processing according toEmbodiment 5 of the present invention;

FIG. 18C is a diagram showing division processing and mapping processingaccording to Embodiment 5 of the present invention;

FIG. 19 is a block diagram of a terminal according to Embodiment 5 ofthe present invention;

FIG. 20 is a block diagram of a terminal according to Embodiment 6 ofthe present invention;

FIG. 21A is a diagram showing DFT output according to Embodiment 6 ofthe present invention;

FIG. 21B is a diagram showing shifting processing according toEmbodiment 6 of the present invention;

FIG. 21C is a diagram showing division processing and mapping processingaccording to Embodiment 6 of the present invention;

FIG. 22A is a diagram showing DFT output according to Embodiment 6 ofthe present invention;

FIG. 22B is a diagram showing shifting processing according toEmbodiment 6 of the present invention;

FIG. 22C is a diagram showing division processing and mapping processingaccording to Embodiment 6 of the present invention;

FIG. 23 is a block diagram of a terminal according to Embodiment 7 ofthe present invention;

FIG. 24 is a diagram showing frequency shifting processing and spaceshifting processing according to Embodiment 7 of the present invention;

FIG. 25 is a diagram showing frequency shifting processing and spaceshifting processing according to Embodiment 7 of the present invention;and

FIG. 26 is a diagram showing shifting processing according to Embodiment8 of the present invention.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. A case will bedescribed below where a terminal provided with a radio communicationapparatus according to the present invention transmits a C-SC-FDMAsignal to a base station.

Embodiment 1

FIG. 1 shows a configuration of terminal 100 according to the presentembodiment.

In terminal 100, radio receiving section 102 receives a control signaltransmitted from a base station (not shown) via antenna 101, appliesreception processing such as down-conversion and A/D conversion to thecontrol signal and outputs the control signal subjected to the receptionprocessing to demodulation section 103. This control signal includesfrequency resource information showing uplink frequency resourcesallocated to each terminal and MCS information showing MCS (Modulationand channel Coding Scheme) set in each terminal.

Demodulation section 103 demodulates the control signal and outputs thedemodulated control signal to decoding section 104.

Decoding section 104 decodes the control signal and outputs the decodedcontrol signal to extraction section 105.

Extraction section 105 extracts frequency resource information directedto terminal 100 included in the control signal inputted from decodingsection 104 and outputs the extracted frequency resource information tocontrol section 106.

Control section 106 receives category information of the terminalincluding a DFT size (the number of DFT points) of a DFT matrix to beused in DFT section 110 and partially orthogonal condition informationshowing a partially orthogonal condition of a C-SC-FDMA signal as inputand also receives frequency resource information reported from the basestation from extraction section 105 as input.

Control section 106 calculates the number of clusters generated bydivision section 111 by dividing an SC-FDMA signal (that is, the outputof DFT section 110) and the cluster size showing a bandwidth of eachcluster based on DFT size information (category information) showing theDFT size of the terminal, partially orthogonal condition information andfrequency resource information reported from the base station. Supposeit is determined in advance between the base station and the terminalthat when an SC-FDMA signal (spectrum) is divided into a plurality ofclusters, the SC-FDMA signal (spectrum) is divided in order from a lowerfrequency portion of the spectrum (smaller output number of DFT section110) or from a higher frequency portion of the spectrum (larger outputnumber of DFT section 110). Control section 106 calculates frequencyresources to which C-SC-FDMA signals (a plurality of clusters) ofterminal 100 are mapped based on the calculated number of clusters andthe cluster size. For example, control section 106 calculates frequencyresources to which clusters are mapped in order from a cluster of alower frequency (cluster with a smaller output number of DFT section110) or a cluster of a higher frequency (cluster with a larger outputnumber of DFT section 110) of the plurality of clusters generatedthrough division. Control section 106 then inputs cluster informationincluding the calculated number of clusters and cluster size to divisionsection 111 and outputs mapping information showing frequency resourcesto which C-SC-FDMA signals (a plurality of clusters) of terminal 100 aremapped to mapping section 112.

Coding section 107 encodes a transmission bit sequence and outputs thecoded transmission bit sequence to modulation section 108.

Modulation section 108 modulates the transmission bit sequence inputtedfrom coding section 107 to generate a symbol sequence and outputs thesymbol sequence generated to multiplexing section 109.

Multiplexing section 109 multiplexes pilot signals and the symbolsequence inputted from modulation section 108. Multiplexing section 109outputs the symbol sequence multiplexed with the pilot signals to DFTsection 110. For example, a CAZAC (Constant Amplitude Zero AutoCorrelation) sequence may be used as the pilot signals. Furthermore,although FIG. 1 adopts a configuration in which the pilot signals andthe symbol sequence are multiplexed before applying DFT processing, aconfiguration in which the pilot signals and the symbol sequence aremultiplexed after applying the DFT processing may also be adopted.

DFT section 110 generates frequency domain signals (SC-FDMA signals) byapplying DFT processing to the time domain symbol sequence inputted frommultiplexing section 109 using a DFT matrix. DFT section 110 outputs thegenerated SC-FDMA signals (spectrum) to division section 111.

Division section 111 divides the SC-FDMA signal (spectrum) inputted fromthe DFT section 110 into a plurality of clusters according to the numberof clusters and the cluster size indicated in the cluster informationinputted from control section 106. To be more specific, division section111 generates a plurality of clusters by dividing the SC-FDMA signal(spectrum) with a bandwidth (partially orthogonal bandwidth)corresponding to a length (vector length) of some of the plurality ofcolumn vectors constituting the DFT matrix used in DFT section 110 andpartially orthogonal to each other. Division section 111 then outputsC-SC-FDMA signals made up of the plurality of clusters generated tomapping section 112. Details of the method of dividing the SC-FDMAsignal (spectrum) in division section 111 will be described later.

Mapping section 112 maps the C-SC-FDMA signals (a plurality of clusters)inputted from division section 111 to frequency resources (subcarriersor RBs) based on mapping information inputted from control section 106.For example, mapping section 112 maps the plurality of clusters makingup the C-SC-FDMA signals to a plurality of discontinuous frequency bandsrespectively. Mapping section 112 then outputs the C-SC-FDMA signalsmapped to the frequency resources to IFFT section 113.

IFFT section 113 generates a time-domain C-SC-FDMA signal by performingIFFT on the plurality of frequency bands inputted from mapping section112 to which the C-SC-FDMA signals are mapped. Here, IFFT section 113inserts 0's in frequency bands other than the plurality of frequencybands to which the C-SC-FDMA signals (plurality of clusters) are mapped.IFFT section 113 then outputs the time-domain C-SC-FDMA signal to CP(Cyclic Prefix) insertion section 114.

CP insertion section 114 adds the same signal as that at the end of theC-SC-FDMA signal inputted from IFFT section 113 to the head of theC-SC-FDMA signal as a CP.

Radio transmitting section 115 applies transmission processing such asD/A conversion, amplification and up-conversion to the C-SC-FDMA signaland transmits the signal subjected to the transmission processing to thebase station via antenna 101.

On the other hand, the base station performs FDE processing ofmultiplying the C-SC-FDMA signals (a plurality of clusters) transmittedfrom each terminal by an FDE weight and combines the C-SC-FDMA signals(the plurality of clusters) after the FDE processing in the frequencydomain. The base station obtains a time domain signal by applying IDFTprocessing to the combined C-SC-FDMA signal.

Furthermore, the base station generates channel quality information(e.g. CQI: Channel Quality Indicator) of each terminal by measuring anSINR (Signal-to-Interference plus Noise power Ratio) for each frequencyband (e.g. subcarrier) between each terminal and the base station usingpilot signals transmitted from each terminal. The base station thenschedules allocation of uplink frequency resources (e.g. PUSCH) of eachterminal using CQI and QoS (Quality of Service) or the like of aplurality of terminals. The base station then reports frequency resourceinformation showing the uplink frequency resource allocation result(that is, the scheduling result) of each terminal to each terminal. Forexample, PF (Proportional Fairness) may be used as an algorithm usedwhen the base station allocates frequency resources to each terminal.

Furthermore, the base station controls the number of clusters and thecluster size using the DFT size and partially orthogonal condition as inthe case of control section 106 of terminal 100 and combines theC-SC-FDMA signals (the plurality of clusters) based on the number ofclusters and the cluster size.

Next, details of the SC-FDMA signal (spectrum) division method bydivision section 111 will be described.

Here, the SC-FDMA signal which is the output of DFT section 110 isconfigured by applying orthogonal frequency spreading to each symbol ofa symbol sequence in a frequency band corresponding to the DFT size(column vector length) of the DFT matrix and code-multiplexing eachsymbol after the orthogonal frequency spreading. Here, assuming the DFTsize is N, the DFT matrix used in DFT section 110 can be expressed byN×N matrix F=[f₀, f₁, . . . f_(N-1)]. Furthermore, f_(i) (i=0 to N−1) isan N×1 column vector having (1/√N)exp(−j2π(i*k)/N) (k=0 to N−1) as ak-th element.

Furthermore, all column vectors f_(i) (i=0 to N−1) are orthogonal toeach other in DFT size N. That is, DFT section 110 multiplies N symbols(e.g. symbols #0 to #N−1) constituting the symbol sequence by respectivecolumn vectors f_(i) (i=0 to N−1) of the DFT matrix, and thereby makesall symbols (symbols #0 to #N−1) orthogonal to each other in anorthogonal bandwidth (that is, bandwidth to which N symbols are mapped)corresponding to column vector length N.

For example, in the case of DFT size N=8, a symbol sequence made up ofeight symbols #0 to #7 as shown in the upper part of FIG. 2 is inputtedto DFT section 110. As shown in the lower part of FIG. 2, DFT section110 frequency-spreads symbols #0 to #7 with column vectors f₀ to f₇ ofthe DFT matrix respectively. DFT section 110 then code-multiplexesfrequency-spread symbols #0 to #7. This allows an SC-FDMA signal havingan orthogonal bandwidth corresponding to DFT size N to be obtained.Furthermore, FIG. 3 shows an example of DFT matrix when DFT size N=8.That is, column vector f_(i) (i=0 to 7) is an 8×1 column vector whichhas (1/√8)exp(−j2π(i*k)/8) as a k-th (where k=0 to 7) element.Furthermore, column vectors f₀ to f₇ are orthogonal to each other in DFTsize N=8.

Here, column vector f_(i) of DFT matrix F is not only orthogonal to allother column vectors in DFT size N but also partially orthogonal to someother column vectors in vector length N′ (where N′<N) which is less thanDFT size (column vector length) N. To be more specific, there is arelationship shown in following equation 1 (partially orthogonalcondition) between vector length N′ where arbitrary two different columnvectors f_(i) and f_(i)′ (where i′≠i) of the plurality of column vectorsconstituting the DFT matrix are partially orthogonal to each other andDFT size (column vector length) N of DFT matrix F. Here, I is a non-zerointeger that satisfies |I|<|i-i′|.

[1] $\begin{matrix}{N^{\prime} = {\frac{I}{{i - i^{\prime}}}N}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

A partially orthogonal condition of column vector f₁ (that is, i=1) andcolumn vector f₅ (that is, i′=5) shown in FIG. 3 will be described as anexample. Since |I|<|i-i′|=|−4|=4, |I| takes a value of one of 1, 2 and3.

When |I|=1, vector length N′=2 from equation 1. Thus, as shown in FIG.4A, column vector f₁ and column vector f₅ are partially orthogonal invector length N′=2, that is, between two elements. For example, as shownin FIG. 4A, column vector f₁ and column vector f₅ are partiallyorthogonal between two elements; the 0-th (k=0) element and first (k=1)element and partially orthogonal between two elements; second (k=2)element and third (k=3) element. The same applies to the fourth (k=4) toseventh (k=7) elements.

Likewise, when |I|=2, vector length N′=4 from equation 1. Thus, as shownin FIG. 4B, column vector f₁ and column vector f₅ are partiallyorthogonal in vector length N′=4, that is, between four elements. Forexample, as shown in FIG. 4B, column vector f₁ and column vector f₅ arepartially orthogonal between four elements of the 0-th (k=0) element tothird (k=3) element and partially orthogonal between four elements ofthe fourth (k=4) element to seventh (k=7) element.

Furthermore, when |I|=3, vector length N′=6 from equation 1. Thus, asshown in FIG. 4C, column vector f₁ and column vector f₅ are partiallyorthogonal in vector length N′=6, that is, between six elements. Forexample, as shown in FIG. 4C, column vector f₁ and column vector f₅ arepartially orthogonal between six elements of the 0-th (k=0) element tofifth (k=5) element and partially orthogonal between six elements of thesecond (k=2) element to seventh (k=7) element.

Here, bandwidth (that is, orthogonal bandwidth of the DFT matrix) Bcorresponding to DFT size N of the DFT matrix is represented byN*B_(sub). Here, B_(sub) shows an orthogonal frequency spacing(subcarrier spacing). Similarly, partially orthogonal bandwidth B′corresponding to vector length N′ (where N′<N) where column vector f_(i)and column vector f_(i)′ are partially orthogonal to each other isrepresented by N′*B_(sub). Thus, the relationship (partially orthogonalcondition) between the orthogonal bandwidth of the DFT matrix, that is,total bandwidth (orthogonal bandwidth) B used for transmission of anSC-FDMA signal and partially orthogonal bandwidth B′ can be expressed byfollowing equation 2.

[2] $\begin{matrix}{B^{\prime} = {{N^{\prime}B_{sub}} = {{\frac{I}{{i - i^{\prime}}}{NB}_{sub}} = {\frac{I}{{i - i^{\prime}}}B}}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

Thus, not only column vectors f_(i) (i=0 to N−1) are orthogonal to eachother in DFT size N of the DFT matrix but also there are column vectorshaving an orthogonal relationship in vector length N′ which is less thanDFT size N.

As described above, when the SC-FDMA signal is divided into a pluralityof clusters, the respective clusters are mapped to discontinuousfrequency bands, and therefore a drastic variation (discontinuous point)of an equalization channel gain is likely to occur at a combining pointof clusters. On the other hand, a variation in the equalization channelgain becomes slower in each cluster by performing FDE processing. Thatis, even when a drastic variation of the equalization channel gain(discontinuous point) occurs (when orthogonality of the DFT matrix in anorthogonal bandwidth of the DFT matrix is lost), it is possible toreduce ISI by maintaining orthogonality within clusters.

Thus, in the present embodiment, division section 111 divides theSC-FDMA signal (spectrum) with partially orthogonal bandwidth B′(=N′*B_(sub)) corresponding to vector length N′ having a partiallyorthogonal relationship with column vector length N of the DFT matrix.

Hereinafter, SC-FDMA signal division methods 1-1 to 1-4 will bedescribed.

<Division Method 1-1>

According to the present division method, division section 111 dividesan SC-FDMA signal with partially orthogonal bandwidth B′ (=N′*B_(sub))corresponding to vector length N′ calculated according to equation 1.

In the following descriptions, suppose the number of clusters is 2, onecluster size is partially orthogonal bandwidth B′ that satisfiesequation 2 (or equation 1), and the other cluster size is differentialbandwidth B″(=B-B′) between orthogonal bandwidth B and partiallyorthogonal bandwidth B′. Furthermore, suppose DFT size N is 8.

Thus, division section 111 divides the SC-FDMA signal (spectrum)inputted from DFT section 110 into two clusters; cluster #0 and cluster#1 as shown in FIG. 5A. To be more specific, division section 111divides the SC-FDMA signal having orthogonal bandwidth B with partiallyorthogonal bandwidth B′ calculated according to equation 2. In otherwords, division section 111 divides the SC-FDMA signal with partiallyorthogonal bandwidth B′ corresponding to vector length N′ calculatedaccording to equation 1. Thus, division section 111 generates cluster #0having partially orthogonal bandwidth B′ and cluster #1 having bandwidthB″ (=B-B′) which is the difference between orthogonal bandwidth B andpartially orthogonal bandwidth B′.

As shown in FIG. 5A, mapping section 112 then maps cluster #0 andcluster #1 to two discontinuous frequency bands respectively.

On the other hand, the base station receives a C-SC-FDMA signal made upof cluster #0 and cluster #1 shown in FIG. 5A. The base station appliesFDE processing to the C-SC-FDMA signal and thereby obtains a C-SC-FDMAsignal after the FDE as shown in FIG. 5B. The base station then combinescluster #0 and cluster #1 after the FDE shown in FIG. 5B and therebygenerates a signal having orthogonal bandwidth B (=B′+B″) of the DFTmatrix as shown in FIG. 5C.

As shown in FIG. 5C, the variation of the equalization channel gainbecomes discontinuous at a combining point between cluster #0 andcluster #1. On the other hand, the variation of the equalization channelgain is slow in each cluster. Thus, ISI between multiplexed symbolscorresponding to column vectors f_(i) and f_(i)′ that satisfy equation 2or equation 1 (that is, between partially orthogonal multiplexedsymbols) is reduced in cluster #0. Thus, in cluster #0 (that is, clusterhaving partially orthogonal bandwidth B′), it is possible to reduce ISIcaused by a drastic variation of the equalization channel gain at thecombining point (dividing point of the SC-FDMA signal) between cluster#0 and cluster #1.

Thus, according to the present division method, although a variation ofthe equalization channel gain becomes discontinuous at a combining pointof a plurality of clusters, it is possible to reduce the loss oforthogonality between multiplexed symbols in a cluster having apartially orthogonal bandwidth. Therefore, according to the presentdivision method, it is possible to reduce ISI caused by a drasticvariation of the equalization channel gain even when the SC-FDMA signalis divided into a plurality of clusters.

<Division Method 1-2>

According to the present division method, division section 111 dividesthe SC-FDMA signal with partially orthogonal bandwidth B′ correspondingto vector length N′ in which (|I|/|i-i′|)⁻¹ in equation 1 is 2 or moreand less than N and at the same time one of divisors of N.

This will be described more specifically below. Here, suppose DFT size Nis 12 and the number of clusters is 2.

When N=12, divisors of N=12, which are 2 or more and less than 12, are2, 3, 4 and 6. Thus, division section 111 selects one of(|I|/|i-i′|)⁻¹=2, 3, 4, 6 which is the reciprocal of (|I|/|i-i′|) shownin equation 1. That is, division section 111 selects one of vectorlengths N′=6, 4, 3 and 2 according to equation 1. That is, column vectorf_(i) and column vector f_(i)′ that satisfy (|I|/|i-i′|)=½, ⅓, ¼ and ⅙respectively in equation 1 are partially orthogonal in vector lengthsN′=6, 4, 3 and 2 respectively.

When, for example, dividing column vector f_(i) (i=0 to 11) with vectorlength N′=6 (that is, when (|I|/|i-i′|)⁻¹=2), division section 111assumes vector length N′ of cluster #0 to be 6 and assumes vector lengthN″ of cluster #1 to be 6 (=N-N′=12-6). That is, division section 111divides the SC-FDMA signal having orthogonal bandwidth B(=N*B_(sub)=12B_(sub)) into cluster #0 having partially orthogonalbandwidth B′ (=N′*B_(sub)=6B_(sub)) and cluster #1 having bandwidth B″(=N″*B_(sub)=6B_(sub)). The same applies to cases where vector lengthN′=4, 3, 2.

Thus, combination (N′, N″) of vector lengths of two clusters (cluster #0and cluster #1) including the cluster of vector length N′ calculatedusing the present division method is one of (6, 6), (4, 8), (3, 9) and(2, 10). That is, all combinations of vector lengths of the two clustersare integers. Therefore, while the DFT size (the number of DFT points)of the DFT matrix takes an integer value of 0 to N−1, vector length N′and vector length N″=(N-N′) that divide column vector f_(i) can alwaysbe integer values without becoming fractions. In other words, partiallyorthogonal bandwidth B′ that divides orthogonal bandwidth B(=N*B_(sub))can always be limited to an integer multiple of B_(sub).

Thus, according to the present division method, it is possible toimprove affinity between DFT processing of outputting an SC-FDMA signalusing DFT size N, which is an integer value, and division processing ofdividing the SC-FDMA signal, which is the output of the DFT processing,into a plurality of clusters while obtaining effects similar to those ofdivision method 1.

<Division Method 1-3>

According to the present division method, division section 111 dividesthe SC-FDMA signal with partially orthogonal bandwidth B′ correspondingto vector length N′, which is a multiple of a prime number.

This will be described more specifically below. For example, divisionsection 111 assumes vector length N′ to be multiple a₀x₀ (wherecoefficient a₀ is an integer equal to or greater than 1) of prime numberx₀. Here, suppose DFT size N is 12 and the number of clusters is 2.Furthermore, suppose prime number x₀=3 and coefficient a₀=3.

Thus, division section 111 assumes vector length N′ of cluster #0 to be9 (=3×3) and vector length N″ of cluster #1 to be 3 (=N-N′=12-9). Thatis, division section 111 divides the SC-FDMA signal having orthogonalbandwidth B (=N*B_(sub)=12B_(sub)) corresponding to DFT size N=12 intocluster #0 having partially orthogonal bandwidth B′(=N′*B_(sub)=9B_(sub)) corresponding to vector length N′=9 and cluster#1 having bandwidth B″ (=N″*B_(sub)=3B_(sub)) corresponding to vectorlength N″=3.

Here, in cluster #0 of vector length N′=9 which is multiple a₀x₀ ofprime number x₀=3, there is a column vector which is orthogonal(hierarchically orthogonal) in vector length 3, 6, 9. For example, inreal parts and imaginary parts of column vectors f₀ to f₁₁ shown in FIG.6, their respective waveforms are orthogonal to each other in vectorlength 3, 6, 9 between column vectors f₀ and f₄, between column vectorsf₀ and f₈, and between column vectors f₄ and f₈. Here, only anorthogonal relationship among vector lengths which are multiples ofprime number x₀=3 is shown. For example, between column vectors f₄ andf₈, vector length 3 matches a one-cycle portion of column vector f₄ anda two-cycle portion of column vector f₈, vector length 6 matches atwo-cycle portion of column vector f₄ and a four-cycle portion of columnvector f₈ and vector length 9 matches a three-cycle portion of columnvector f₄ and a six-cycle portion of column vector f₈.

That is, column vectors f₀, f₄ and f₈ of 12 column vectors f₀ to f₁₁ incluster #0 (vector length N′=9) have a hierarchically orthogonalrelationship in which those column vectors are orthogonal to each otherin a cycle of vector length 3, 6, 9. Thus, in cluster #0 (vector lengthN′=9), ISI is reduced between column vectors f₀, f₄ and f₈ (e.g.multiplexed symbols #0, #4, #8) of 12 column vectors f₀ to f₁₁ (e.g.multiplexed symbols #0 to #11) shown in FIG. 6.

Thus, according to the present division method, division section 111divides the SC-FDMA signal with partially orthogonal bandwidth B′corresponding to vector length N′ which is multiple a₀x₀ of prime numberx₀, and can thereby generate a cluster including more multiplexedsymbols which are hierarchically orthogonal in a cycle of a multiple(x₀, 2x₀, . . . , a₀x₀) of prime number x₀. That is, it is possible toproduce more multiplexed symbols (column vectors) which are partiallyorthogonal to each other in cluster size of clusters generated bydividing the SC-FDMA signal. In other words, by reducing multiplexedsymbols (column vectors) which are not partially orthogonal to eachother in cluster size of clusters generated by dividing the SC-FDMAsignal, it is possible to reduce ISI caused by the loss of orthogonalitybetween multiplexed symbols which are not partially orthogonal to eachother.

Furthermore, according to the present division method, coefficient a₀ isthe only information that needs to be reported from the base station toterminal 100 as control information on the division of the SC-FDMAsignal (spectrum), and it is thereby possible to reduce the amount ofinformation required to report the control information.

A case has been described in the present division method where divisionsection 111 divides the SC-FDMA signal with partially orthogonalbandwidth B′ corresponding to vector length N′ which is a multiple ofone prime number. However, in the present invention, for example,division section 111 may also divide the SC-FDMA signal with partiallyorthogonal bandwidth B′ corresponding to vector length N′ which is amultiple of a product of two or more prime numbers.

For example, division section 111 assumes vector length N′ to be amultiple (e.g. b₀(x₀*x₁)) (where b₀ is an integer equal to or greaterthan 1) of a product (e.g. x₀*x₁) of at least two prime numbers (two ormore prime numbers) of prime numbers x₀, x₁, x₂, . . . . Thus, thecluster having partially orthogonal bandwidth B′ corresponding to vectorlength N′=b₀(x₀*x₁) can include multiplexed symbols (column vectors)which are hierarchically partially orthogonal to each other in a cycleof a multiple (x₀, 2x₀, . . . , b₀x₀) of prime number x₀ and multiplexedsymbols (column vectors) which are hierarchically partially orthogonalto each other in a cycle of a multiple (x₁, 2x₁, . . . , b₀x₁) of primenumber x₁. That is, as the minimum division unit (e.g. x₀*x₁) of theSC-FDMA signal increases, it is possible to increase the number ofmultiplexed symbols (column vectors) which are partially orthogonal toeach other in cluster size with the cluster having partially orthogonalbandwidth B′ corresponding to vector length N′=b₀(x₀*x₁). It is therebypossible to further reduce ISI caused by the loss of orthogonalitybetween multiplexed symbols (column vectors).

When two or more prime numbers are selected, it is preferable to selectprime numbers in order from a smaller prime number (2, 3, 5, 7, . . . ).Thus, it is possible to produce more multiplexed symbols (columnvectors) which are hierarchically orthogonal to each other in a cycle ofa multiple of a prime number in a cluster having partially orthogonalbandwidth B′ and further reduce ISI caused by the loss of orthogonalitybetween multiplexed symbols (column vectors).

<Division Method 1-4>

In the present division method, division section 111 divides an SC-FDMAsignal having partially orthogonal bandwidth B′ corresponding to vectorlength N′ which is a power of a prime number.

This will be described more specifically below. For example, divisionsection 111 assumes column vector length N′ to be power x₀ ^(a0) (wherea₀ is an integer equal to or greater than 1) of prime number x₀. Here,suppose DFT size N is 12 and the number of clusters is 2 as in the caseof division method 1-3. Furthermore, suppose prime number x₀=2 andcoefficient a₀=3.

Thus, for example, division section 111 assumes vector length N′ ofcluster #0 to be 8 (=2³) and assumes vector length N″ of cluster #1 tobe 4 (=N-N′=12-8). That is, division section 111 divides an SC-FDMAsignal having orthogonal bandwidth B (=N*B_(sub)=12B_(sub))corresponding to DFT size N=12 into cluster #0 having partiallyorthogonal bandwidth B′ (=N′*B_(sub)=8B_(sub)) corresponding to vectorlength N′=8 and cluster #1 having bandwidth B″ (=N″*B_(sub)=4B_(sub))corresponding to vector length N″=4.

Here, there are column vectors which are orthogonal to each other invector lengths of 2, 4, 8 in cluster #0 having vector length N′=8 whichis power x₀ ^(a0) of prime number x₀=2. For example, in real parts andimaginary parts of column vectors f₀ to f₁₁ shown in FIG. 7, theirrespective waveforms are orthogonal to each other in vector length 2, 4,8 between column vectors f₀ and f₃, between column vectors f₀ and f₆ andbetween column vectors f₃ and f₆ as in the case of division method 1-3(FIG. 6). Here, only an orthogonal relationship between vector lengthswhich are powers of prime number x₀=2 is shown.

That is, column vectors f₀, f₃, f₆ of 12 column vectors f₀ to f₁₁ incluster #0 (vector length N′=8) have a hierarchic orthogonalrelationship in which those column vectors are orthogonal to each otherin a cycle of vector length 2, 4, 8. Thus, in cluster #0 (vector lengthN′=8), ISI is reduced between column vectors f₀, f₃, f₆ (e.g.multiplexed symbols #0, #3, #6) of 12 column vectors f₀ to f₁₁ (e.g.multiplexed symbols #0 to #11) shown in FIG. 7.

Thus, according to the present division method, division section 111divides the SC-FDMA signal with partially orthogonal bandwidth B′corresponding to vector length N′ which is power x₀ ^(a0) of primenumber x₀, and can thereby generate clusters including more multiplexedsymbols (column vectors) which are hierarchically orthogonal in a cycleof a power (x₀, x₀ ², . . . x₀ ^(a0)) of prime number x₀. Thus, it ispossible to reduce ISI caused by the loss of orthogonality betweenmultiplexed symbols (column vectors) which are not partially orthogonalto each other in cluster size of clusters generated by dividing theSC-FDMA signal as in the case of division method 1-3.

Furthermore, according to the present division method, coefficient a₀ isthe only information that needs to be reported from the base station toterminal 100 as control information on the division of the SC-FDMAsignal (spectrum) and it is thereby possible to reduce the amount ofinformation required to report the control information as in the case ofdivision method 1-3.

A case has been described in the present division method where divisionsection 111 divides the SC-FDMA signal with partially orthogonalbandwidth B′ corresponding to vector length N′ which is a power of oneprime number. However, in the present invention, for example, divisionsection 111 may also divide the SC-FDMA signal with a partiallyorthogonal bandwidth B′ corresponding to vector length N′ which is apower of a product of two or more prime numbers.

For example, division section 111 assumes vector length N′ to be a power(e.g. (x₀*x₁)^(b0)) (where b₀ is an integer equal to or greater than 1)of a product (e.g. x₀*x₁) of at least two prime numbers (two or moreprime numbers) of prime numbers x₀, x₁, x₂, . . . . Thus, the clusterhaving partially orthogonal bandwidth B′ corresponding to vector lengthN′=(x₀*x₁)^(b0) can include multiplexed symbols (column vectors) whichare hierarchically partially orthogonal to each other in a cycle of apower (x₀, x₀ ², . . . , x₀ ^(b0)) of prime number x₀ and multiplexedsymbols (column vectors) which are hierarchically partially orthogonalto each other in a cycle of a power (x₁, x₁ ², . . . , x₁ ^(b0)) ofprime number x₁. That is, as the minimum division unit (e.g. x₀*x₁) ofthe SC-FDMA signal increases, it is possible to increase the number ofmultiplexed symbols (column vectors) which are partially orthogonal toeach other in cluster size of the cluster having partially orthogonalbandwidth B′ corresponding to vector length N′=(x₀*x₁)^(b0). It isthereby possible to further reduce ISI caused by the loss oforthogonality between multiplexed symbols (column vectors).

Furthermore, in the present invention, division section 111 may alsoassume vector length N′ to be a multiple (e.g. p₀(x₀*x₁)^(b0))) (wherep₀ is an integer equal to or greater than 1) of a power (e.g.(x₀*x₁)^(b0)) of a product (e.g. x₀*x₁) of at least two prime numbers(two or more prime numbers) of prime numbers x₀, x₁, x₂, . . . . Effectssimilar to those of the present division method may be obtained in thiscase, too.

Furthermore, in the present invention, division section 111 may alsoassume vector length N′ to be product x₀ ^(c0)*x₁ ^(c1)* . . . of atleast two (two or more) powers x₀ ^(c0), x₁ ^(c1), . . . (c₀, c₁, . . .is an integer equal to or greater than 0, where, at least one of c₀, c₁,. . . is an integer equal to or greater than 1) of prime numbers x₀, x₁,. . . . Effects similar to those of the present division method may beobtained in this case, too. Here, in FFT (Fast Fourier Transform) thatrealizes processing equivalent to that of DFT by a smaller amount ofcalculations, a product of a power of a certain value may be used as theFFT size (the number of FFT points). Thus, when using FFT as asubstitute for DFT, it is possible to improve affinity between FFTprocessing and division processing of the SC-FDMA signal by using aproduct of powers of prime numbers x₀ ^(c0)*x₁ ^(c1)* . . . as vectorlength N′ for dividing column vector length N. Furthermore, divisionsection 111 may also assume vector length N′ to be multiple p₀ (x₀^(c0)*x₁ ^(c1)* . . . ) (where p₀ is an integer equal to or greaterthan 1) of a product of powers of prime numbers x₀ ^(c0)*x₁ ^(c1)* . . ..

When two or more prime numbers are selected, it is preferable to selectprime numbers in order from a smaller prime number (2, 3, 5, 7, . . . ).It is thereby possible to produce more multiplexed symbols (columnvectors) which are hierarchically partially orthogonal to each other ina cycle of a power of a prime number in clusters having partiallyorthogonal bandwidth B′ and further reduce ISI caused by the loss oforthogonality between multiplexed symbols (column vectors).

SC-FDMA signal division methods 1-1 to 1-4 through division section 111have been described so far.

Thus, even when dividing an SC-FDMA signal into a plurality of clustersand mapping the plurality of clusters to discontinuous frequency bandsrespectively, the present embodiment can reduce ISI caused by the lossof orthogonality of the DFT matrix by dividing the SC-FDMA signal with apartially orthogonal bandwidth.

Thus, the present embodiment reduces ISI caused by the loss oforthogonality of the DFT matrix, and can thereby improve transmissioncharacteristics without deteriorating data transmission efficiency evenwhen using high-level M-ary modulation such as 64 QAM which has a veryshort Euclidian distance between signal points.

A case has been described in the present embodiment where a terminaldivides an SC-FDMA signal into a plurality of clusters so that abandwidth of one cluster (here, cluster #0) is a partially orthogonalbandwidth. However, the terminal in the present invention may alsodivide the SC-FDMA signal into a plurality of clusters using one ofdivision methods 1-1 to 1-4 so that bandwidths of all of the pluralityof clusters are partially orthogonal bandwidths. Thus, it is possible toincrease the number of multiplexed symbols having a partially orthogonalrelationship with each other in all clusters and thereby reduce ISIcluster by cluster.

Furthermore, in the present embodiment, the terminal may performfrequency interleaving for each frequency band (or cluster) having apartially orthogonal bandwidth as shown in FIG. 8. To be more specific,when division section 111 divides the SC-FDMA signal into cluster #0 andcluster #1 as shown in the upper part of FIG. 8, an interleaving section(not shown) performs frequency interleaving in units of partiallyorthogonal bandwidth. That is, the interleaving section performsfrequency interleaving on a first-half portion of cluster #0 havingpartially orthogonal bandwidth B₀′, a last-half portion of cluster #0having partially orthogonal bandwidth B₀′ and cluster #1 havingpartially orthogonal bandwidth B₁′. Thus, it is possible to furtherimprove the frequency diversity effect while reducing the loss oforthogonality in the clusters as in the case of the present embodiment.

Furthermore, a case has been described in the present embodiment wherethe base station reports only frequency resource information to terminal100 every time the base station communicates with terminal 100 andterminal 100 calculates cluster information (the number of clusters andthe cluster size) based on category information and partially orthogonalcondition information (equation 1 and equation 2) reported beforehand.However, in the present invention, for example, the base station mayreport all frequency resource information and cluster information (thenumber of clusters and the cluster size) to terminal 100 every time thebase station communicates with terminal 100 and terminal 100 may dividethe SC-FDMA signal based on the received frequency resource informationand cluster information.

Furthermore, for example, the base station may also report frequencyresource information showing frequency bands allocated in considerationof the number of clusters and the cluster size to terminal 100. To bemore specific, the base station (scheduler of the base station) performsscheduling and thereby performs allocation processing of allocatingfrequency bands of partially orthogonal bandwidth B′ that includes afrequency band of terminal 100 showing a maximum SINR in a certainfrequency band (subcarrier) and satisfies equation 2 (or equation 1) onterminal 100. That is, the base station allocates frequency bands ofpartially orthogonal bandwidth B′ calculated according to equation 2 (orequation 1) to a plurality of clusters constituting a C-SC-FDMA signalof terminal 100. The base station allocates frequency resources of theC-SC-FDMA signal made up of a plurality of clusters having a partiallyorthogonal bandwidth by repeatedly performing the above describedallocation processing in different frequency bands. The base stationthen reports frequency resource information showing the frequencyresource allocation result of the C-SC-FDMA signal of terminal 100 toterminal 100. The base station also performs the above describedfrequency resource allocation processing on terminals other thanterminal 100. This allows the base station to schedule the allocation offrequency resources to all terminals locating in the cell of the basestation. Furthermore, terminal 100 may map the C-SC-FDMA signalaccording to the frequency band shown in the frequency resourceinformation reported from the base station. This allows terminal 100 todivide SC-FDMA into a plurality of clusters, map the plurality ofclusters to frequency bands having a partially orthogonal bandwidth andcan thereby have effects similar to those of the present embodiment.

Embodiment 2

The present embodiment will describe a case where MIMO (Multi-InputMulti-Output) transmission, which is one of transmission techniques forrealizing high-speed, large-volume data transmission, is used. The MIMOtransmission technique provides a plurality of antennas for both a basestation and a terminal, provides a plurality of propagation paths(streams) in a space between radio transmission/reception, spatiallymultiplexes the respective streams, and can thereby increase throughput.

This will be described more specifically below. FIG. 9 shows aconfiguration of terminal 200 according to the present embodiment.Terminal 200 is provided with two antennas (antennas 101-1 and 101-2)that transmit C-SC-FDMA signals (a plurality of clusters) using twostreams (stream #1 and stream #2).

Furthermore, terminal 200 includes C-SC-FDMA processing sections 201-1and 201-2 made up of coding section 107, modulation section 108,multiplexing section 109, DFT section 110 and division section 111,respectively provided for antennas 101-1 and 101-2.

Furthermore, terminal 200 also includes transmission processing sections203-1 and 203-2 made up of mapping section 112, IFFT section 113, CPinsertion section 114 and radio transmitting section 115, respectivelyprovided for antennas 101-1 and 101-2.

C-SC-FDMA processing sections 201-1 and 201-2 generate C-SC-FDMA signals(a plurality of clusters) by applying processing similar to that bycoding section 107 to division section 111 in Embodiment 1 totransmission bit sequences inputted respectively. C-SC-FDMA processingsections 201-1 and 201-2 then output the C-SC-FDMA signals generated toprecoding section 202 respectively.

Precoding section 202 receives different spatial precoding matrixes (PM)for each identical frequency band having a partially orthogonalbandwidth or for each identical cluster of the partially orthogonalbandwidth from control section 106 as input. That is, precoding section202 uses the same spatial precoding matrix for each identical frequencyband having a partially orthogonal bandwidth or for each identicalcluster having a partially orthogonal bandwidth. Here, precodinginformation showing the spatial precoding matrix is reported from a basestation to terminal 200. For example, the precoding information shows anumber indicating each spatial precoding matrix and control section 106may calculate each spatial precoding matrix based on the numberindicated in the precoding information.

Precoding section 202 multiplies the C-SC-FDMA signals inputted fromC-SC-FDMA processing sections 201-1 and 201-2 by the spatial precodingmatrix respectively. Here, precoding section 202 multiplies theC-SC-FDMA signals mapped to frequency bands having the same partiallyorthogonal bandwidth or clusters having the same partially orthogonalbandwidth by the same spatial precoding matrix in each of the pluralityof streams. Precoding section 202 then outputs the precoded C-SC-FDMAsignals to corresponding transmission processing sections 203-1 and203-2 for each stream.

Transmission processing sections 203-1 and 203-2 apply processingsimilar to that of mapping section 112 to radio transmitting section 115of Embodiment 1 to the precoded C-SC-FDMA signals inputted respectivelyand transmit the C-SC-FDMA signals after the transmission processing tothe base station via antennas 101-1 and 101-2 respectively.

Next, details of the precoding processing by precoding section 202 ofterminal 200 will be described.

First, a case will be described where the same spatial precoding matrixis used for each partially orthogonal band. For example, in FIG. 10A,each division section 111 (FIG. 9) of C-SC-FDMA processing sections201-1 and 201-2 divides an SC-FDMA signal into cluster #0 having abandwidth twice partially orthogonal bandwidth B₀′ and cluster #1 havingpartially orthogonal bandwidth B₁′.

Therefore, precoding section 202 multiplies cluster #0 and cluster #1transmitted by the same spatial precoding matrix for every partiallyorthogonal bandwidth using stream #1 and stream #2. To be more specific,as shown in FIG. 10A, precoding section 202 uses the same spatialprecoding matrix PM #0 for both stream #1 and stream #2 in one partiallyorthogonal bandwidth B₀′ of cluster #0 and uses the same spatialprecoding matrix PM #1 for both stream #1 and stream #2 in the otherpartially orthogonal bandwidth B₀′. Furthermore, precoding section 202uses the same spatial precoding matrix PM #2 for both stream #1 andstream #2 in cluster #1 having partially orthogonal bandwidth B₁′.

Next, a case will be described where the same spatial precoding matrixis used for each cluster. For example, in FIG. 10B, each divisionsection 111 (FIG. 9) of C-SC-FDMA processing sections 201-1 and 201-2divides an SC-FDMA signal into cluster #0 having partially orthogonalbandwidth B₀′ and cluster #1 having partially orthogonal bandwidth B₁′.

Precoding section 202 then multiplies cluster #0 and cluster #1transmitted using stream #1 and stream #2 by the same spatial precodingmatrix for each cluster. To be more specific, as shown in FIG. 10B,precoding section 202 uses the same spatial precoding matrix PM #0 forboth stream #1 and stream #2 in cluster #0 having partially orthogonalbandwidth B₀′. Furthermore, precoding section 202 uses the same spatialprecoding matrix PM #2 for both stream #1 and stream #2 in cluster #1having partially orthogonal bandwidth B₁′.

Thus, for example, in FIG. 10A, between cluster #0 of stream #1 andcluster #1 of stream #2, it is possible to reduce ISI by maintainorthogonality between multiplexed symbols (column vectors) in therespective clusters in the frequency domain as in the case of Embodiment1, while in the spatial domain, it is possible to maintain orthogonalitybetween them using spatial precoding matrixes (e.g. unitary matrixes)orthogonal to each other. That is, it is possible to further reduce ISIbetween cluster #0 of stream #1 and cluster #1 of stream #2 (that is,between clusters transmitted with different frequency bands anddifferent streams). The same applies between cluster #1 of stream #1 andcluster #0 of stream #2.

That is, when using the MIMO transmission technique, it is possible toreduce ISI between different streams and between different frequencybands by using the same spatial precoding matrix for each identicalpartially orthogonal bandwidth (or each cluster) in different streams.

By this means, the present embodiment can reduce ISI in the frequencydomain by dividing the SC-FDMA signal with a partially orthogonalbandwidth as in the case of Embodiment 1 and further reduce ISI in thespatial domain by using a spatial precoding matrix for each partiallyorthogonal bandwidth.

Although a case has been described in the present embodiment where twostreams are used, the number of streams is not limited to two but thepresent invention may also be applied to cases where three or morestreams are used.

Furthermore, the present embodiment is applicable to both single user(SU)-MIMO transmission (that is, MIMO transmission between a pluralityof antennas of one base station and a plurality of antennas of oneterminal) and multiuser (MU)-MIMO transmission (that is, MIMOtransmission between a plurality of antennas of one base station and aplurality of antennas of a plurality of terminals).

Furthermore, in the present embodiment, when FSTD (Frequency SwitchedTransmit Diversity) is used, the terminal may switch betweentransmitting antennas for each frequency band (or cluster) having apartially orthogonal bandwidth. For example, as shown in FIG. 11, whenthe number of transmitting antenna is 3 (antennas #0 to #2) and thenumber of clusters is 3 (clusters #0 to #2), the first half part ofcluster #0 having partially orthogonal bandwidth B₀′ may be transmittedfrom antenna #0, the second half part of cluster #0 having partiallyorthogonal bandwidth B₀′ may be transmitted from antenna #1, cluster #1having partially orthogonal bandwidth B₁′ may be transmitted fromantenna #0 and cluster #2 having partially orthogonal bandwidth B₂′ maybe transmitted from antenna #2. Thus, by switching between transmittingantennas based on the unit of frequency bands (or clusters) having apartially orthogonal bandwidth in FSTD, it is possible to receive afading variation which differs among frequency bands (B₀′ to B₂′) havingpartially orthogonal bandwidths. Therefore, it is possible to obtain aspace diversity effect while maintaining orthogonality within afrequency band having partially orthogonal bandwidths.

Embodiment 3

A case has been described in Embodiment 2 where when FSTD (FrequencySwitched Transmit Diversity) is used, a terminal switches betweentransmitting antennas for each frequency band (or cluster) having apartially orthogonal bandwidth. Furthermore, in this case, a case hasbeen described where a plurality of clusters are mapped tonon-continuous frequency bands when viewed in the frequency domain ofall transmitting antennas. By contrast, in the present embodiment, whenusing FSTD that switches between transmitting antennas for eachfrequency band (or cluster) having a partially orthogonal bandwidth, aterminal maps a plurality of clusters to continuous frequency bands whenviewed in the frequency domain of all transmitting antennas.

That is, when FSTD is used in Embodiment 2, as shown in FIG. 11,clusters having partially orthogonal bandwidths mapped to the respectiveantennas are mapped to non-continuous frequency bands and a plurality ofclusters are mapped to non-continuous frequency bands when also viewedin frequencies of all antennas. To be more specific, there is aninter-antenna vacant frequency band between cluster #0 of antenna #1 andcluster #1 of antenna #0 in FIG. 11. Likewise, there is also aninter-antenna vacant frequency band between cluster #1 of antenna #0 andcluster #2 of antenna #2. Furthermore, in FIG. 11, no cluster is mappedto any inter-antenna vacant frequency band and a plurality of clustersare mapped to non-continuous frequency bands when also viewed in thefrequency domain of all antennas.

On the other hand, in the present embodiment, when FSTD is used, asshown in FIG. 12, clusters having partially orthogonal bandwidths to bemapped to the respective antenna (space resources) are mapped tonon-continuous frequency bands as in the case of Embodiment 2. On theother hand, as shown in FIG. 12, a plurality of clusters havingpartially orthogonal bandwidths to be mapped to the respective antennas(space resources) are mapped to continuous frequency bands when viewedin the frequency domain of all antennas. That is, in FIG. 12, there isno vacant frequency band between any clusters; between cluster #A ofantenna #0 (space resource #0) and cluster #B of antenna #1 (spaceresource #1), between cluster #B of antenna #1 (space resource #1) andcluster #C of antenna #0 (space resource #0) and between cluster #C ofantenna #0 (space resource #0) and cluster #D of antenna #2 (spaceresource #2). That is, when viewed in the frequency domain of allantennas, a plurality of clusters having partially orthogonal bandwidthsare mapped to continuous frequency bands.

That is, when viewed in the frequency domain of each antenna, even whenC-SC-FDMA signals (a plurality of clusters having partially orthogonalbandwidths) are mapped to non-continuous frequency bands, if C-SC-FDMAsignals are mapped to continuous frequency bands when viewed in thefrequency domain of all antennas, it is possible to further obtain spacediversity effects while maintaining orthogonality within a frequencyband having partially orthogonal bandwidths as in the case of Embodiment2. Furthermore, the receiving apparatus (base station) side can performreception processing in the same way as when the transmitting apparatus(terminal) side transmits SC-FDMA signals to continuous frequency bands.Thus, according to the present embodiment, the receiving apparatus (basestation) can obtain space diversity effects while maintainingorthogonality within a frequency band of partially orthogonal bandwidthswithout being aware of non-continuous mapping processing betweenantennas (between space resources) of the transmitting apparatuses.

The present invention may also use a method of mapping a plurality ofclusters having partially orthogonal bandwidths so as to rotate theantenna axis (or antenna direction, space resource region) in thefrequency domain as the method of mapping the plurality of clustershaving partially orthogonal bandwidths to the plurality of antennas.FIG. 13 shows a case where the terminal maps a plurality of clusters(clusters #A, #B, #C, #D) to antennas #0 to #2 (space resources #0 to#2) in such a way that the clusters rotate in the same direction of theantenna axis (or antenna direction, space resource region) in order froma low frequency to a high frequency. To be more specific, as shown inFIG. 13, the terminal maps cluster #A to antenna #0 (space resource #0),maps cluster #B to antenna #1 (space resource #1), maps cluster #C toantenna #2 (space resource #2) and maps cluster #D to antenna #0 (spaceresource #0). That is, in FIG. 13, the terminal maps clusters #A, #B, #Cand #D so as to rotate in the same direction of the antenna axis (orantenna direction, space resource region) (that is, in the rotatingdirection in which the antenna number (space resource number) cyclicallyincreases as the frequency increases) in order of antennas #0, #1, #2,#0, . . . . Furthermore, as shown in FIG. 13, four clusters #A, #B, #Cand #D are mapped to continuous frequency bands when viewed in thefrequency domain of all antennas as in the case of FIG. 12.

Thus, since the frequency domain of antennas (space resources) to whicha plurality of clusters are mapped is set cyclically, only one piece offrequency resource allocation information (continuous frequencyresources or non-continuous frequency resources) needs to be reported tothe plurality of antennas as frequency resource allocation informationwhen the plurality of clusters are mapped to the frequency domain of theplurality of antennas. Thus, it is possible to obtain effects similar tothe present embodiment while reducing the amount of information requiredto allocate frequency resources to the respective antennas. By sharinginformation on the rotating direction on the antenna axis (spaceresource region) (e.g. the rotating direction in which the antennanumber (space resource number, layer number) cyclically increases(decreases) as the frequency increases (decreases)) between the basestation and the terminal, only one piece of frequency resourceallocation information needs to be reported to the plurality of antennasas control information from the base station to the terminal.

FIG. 13 has described a case with the rotating direction in which theantenna number (space resource number) of the antenna to which eachcluster is mapped cyclically increases as the frequency increases as anexample. However, in the present invention, the rotating direction ofthe antenna axis (space resource region) in the frequency domain mayalso be a rotating direction in which the antenna number (space resourcenumber, layer number) cyclically decreases as the frequency increases.

Furthermore, the rotating direction of the antenna axis (space resourceregion) may also be switched for every certain frequency band (subbandunit made up of a plurality of subcarriers, resource block unit orresource block group unit or the like). Alternatively, the rotatingdirection of the antenna axis (space resource region) may also beswitched for every certain time unit (symbol unit, slot unit, subframeunit or number of retransmissions is performed or the like).Alternatively, the rotating direction of the antenna axis (spaceresource region) may also be switched for every certain time-frequencyunit made up of two-dimensional resources of the time domain and thefrequency domain. For example, a frequency band allocated to a terminalmay be divided into two portions and a plurality of clusters havingpartially orthogonal bandwidths may be mapped to a plurality of antennasin the rotating direction in which the antenna number of an antenna towhich each cluster is mapped cyclically increases as the frequencyincreases in one frequency band and in the rotating direction in whichthe antenna number of an antenna to which each cluster is mappedcyclically decreases as the frequency increases in the other frequencyband. Furthermore, when, for example, one codeword made up of aplurality of symbols is mapped over two slots (e.g. first slot andsecond slot), a plurality of clusters having partially orthogonalbandwidths may be mapped to a plurality of antennas in the rotatingdirection in which the antenna number of an antenna to which eachcluster is mapped cyclically increases as the frequency increases in thefirst slot and in the rotating direction in which the antenna number ofan antenna to which each cluster is mapped cyclically decreases as thefrequency increases in the second slot. Thus, it is possible to increaserandomness of channels in the frequency domain (or time domain) whilemaintaining a partially orthogonal relationship in each cluster andthereby further improve the diversity effect.

Furthermore, a case has been described in FIG. 13 where the antennanumber of an antenna to which each cluster is mapped is rotated in thesame direction of the antenna axis (or antenna direction, space resourceregion) in order from a lowest frequency and a plurality of clusters aremapped to the antennas (space resources). However, the present inventionmay also be adapted so that the antenna number of an antenna to whicheach cluster is mapped is rotated in the same direction of the antennaaxis (or antenna direction, space resource region) in order from ahigher frequency and a plurality of clusters are mapped to the antennas(space resources).

Furthermore, a case has been described in FIG. 13 where the terminalmaps the clusters to a plurality of antennas over continuous frequencybands while rotating four clusters #A to #D among different antennas(antennas #0 to #2) as an example. However, in the present invention,the terminal may also map the clusters to non-continuous frequency bandsover a plurality of antennas while rotating the plurality of clustersamong different antennas in the same way as in FIG. 11. That is, in FIG.13, there may be a vacant frequency band (frequency band to which nocluster is allocated) between any clusters; between cluster #A ofantenna #0 and cluster #B of antenna #1, between cluster #B of antenna#1 and cluster #C of antenna #2 and between cluster #C of antenna #2 andcluster #D of antenna #0.

Embodiment 4

<Division method 1-4> of Embodiment 1 has described a case wheredivision section 111 (FIG. 1) divides an SC-FDMA signal with partiallyorthogonal bandwidth B′ corresponding to vector length N′ in (1) to (5)shown below.

(1) Power of prime number x₀:

-   -   N′=x₀ ^(a0) (where a₀ is an integer equal to or greater than 1)

(2) Power of a product of at least two prime numbers (two or more primenumbers) of prime numbers x₀, x₁, x₂, . . . :

N′=(x₀*x₁)^(b0) (where b₀ is an integer equal to or greater than 1)

(3) A multiple of a power of a product of at least two prime numbers(two or more prime numbers) of prime numbers x₀, x₁, x₂, . . . :

N′=p₀(x₀*x₁)^(b0) (where p₀ is an integer equal to or greater than 1)

(4) A product of at least two (two or more) of powers x₀ ^(c0), x₁^(c1), . . . (c₀, c₁, . . . is an integer equal to or greater than 0,however at least one of c₀, c₁, . . . is an integer equal to or greaterthan 1) of prime numbers x₀, x₁, . . . :

-   -   N′=x₀ ^(c0)*x₁ ^(c1)* . . .

(5) A multiple of a product of powers of prime numbers x₀ ^(c0)*x₁^(c1)* . . . :

N′=p₀(x₀ ^(c0)*x₁ ^(c1)* . . . ) (where p₀ is an integer equal to orgreater than 1)

Here, a product of prime numbers (e.g. (x₀*x₁)) or a product of powersof prime numbers (e.g. (x₀ ^(c0)*x₁ ^(c1))) is represented by a finitenumber of values equal to or greater than 2 (e.g. two numerical valuesof x₀ and x₁ or two numerical values of x₀ ^(c0) and x₁ ^(c1)). That is,when a prime number which is the base of a power is represented by x_(i)(i=0 to M−1) and the exponent of the power is represented by c_(i) (i=0to M−1), M becomes a finite value showing an integer of 2 or more.

The present embodiment is different from <division method 1-4> inEmbodiment 1 in that coefficients of powers (that is, exponents ofpowers) c₀, c₁, . . . , c_(M-1) are made related to the bases of thepowers (that is, prime numbers) x₀, x₁, . . . , x_(M-1) in the divisionmethod using vector length N′ in above (4) and vector length N′ in (5)described in <division method 1-4> of Embodiment 1.

To be more specific, when the base (prime number) of power isrepresented by x_(i) (i=0 to M−1) and the exponent of the power thereofis represented by c_(i) (i=0 to M−1), control section 106 (FIG. 1) ofterminal 100 according to the present embodiment sets the value of c_(i)corresponding to x_(i) to a value equal to or smaller than the exponentof the power having a greater base for the product of powers x₀ ^(C0)*x₁^(c1)* . . . *x_(M-1) ^(cM-1) as the value of x_(i) increases. That is,when the base (prime number) of the power has a relationship ofx_(i)<x_(i′) (i≠i′), control section 106 sets exponent c_(i)corresponding to base of power x_(i) so as to be c_(i)≧c_(i′)(i≠i′).Therefore, when the bases of power have a relationship of x₀<x₁<x₂< . .. <x_(M-1), control section 106 sets exponents corresponding to thebases of powers so as to have a relationship of c₀≧c₁≧c₂≧ . . .≧c_(M-1). Control section 106 calculates vector length N′=x₀ ^(c0)*x₁^(c1)* . . . *x_(M-1) ^(cM-1) (corresponds to vector length N′ in (4) of<division method 1-4>) or vector length N′=p₀(x₀ ^(c0)*x₁ ^(c1)* . . .*x_(M-1) ^(cM-1)) (corresponds to vector length N′ in (5) of <divisionmethod 1-4>). Division section 111 then divides the SC-FDMA signal withvector length N′ or partially orthogonal bandwidth B′ correspondingthereto. That is, division section 111 divides the SC-FDMA signal with apartially orthogonal bandwidth corresponding to vector length N′ wherevalue of exponent c_(i) of certain power x_(i) ^(ci) (i is one of 0 to(M−1)) among a plurality of powers (x₀ ^(c0), x₁ ^(c1), . . . , x_(M-1)^(cM-1)) constituting a product (x₀ ^(c0)*x₁ ^(c1)* . . . *x_(M-1)^(cM-1)) of powers representing vector length N′ becomes equal to orsmaller than value of exponent c_(i′) of another power x_(i′) ^(ci′)having a smaller base than base x₁ of the certain power x_(i) ^(c1)(that is, a power corresponding to x_(i′)<x_(i), where i′≠i) and becomesequal to or greater than value of exponent c_(i″) of another powerx_(i″) ^(ci″) having a base greater than base x_(i) of certain powerx_(i) ^(ci) (that is, a power corresponding to x_(i″)>x_(i), wherei″≠i). Mapping section 112 maps the plurality of clusters generated bydividing the SC-FDMA signal to non-continuous frequency bands.

Thus, it is possible to increase the number of combinations of partiallyorthogonal column vectors having a shorter cycle in each cluster of apartially orthogonal band (length) represented by equation 1 andequation 2 and thereby further reduce ISI.

Hereinafter, a case will be described as an example where vector lengthN′ (=x₀ ^(c0)*x₁ ^(c1)* . . . *x₁ ^(cM-1)) in (4) of <division method1-4> of Embodiment 1 is used. Here, suppose M=3 and the base of eachpower is x₀=2, x₁=3, x₂=5 (that is, x₀<x₁<x₂). Furthermore, a comparisonwill be made in the number of column vectors partially orthogonal toeach other in clusters in the case where the exponent is c₀<c₁<c₂(example 1) and c₀≧c₁≧c₂ (example 2, that is, the present embodiment).

First, a case with c₀=0, c₁=1, c₂=2 (c₀<c₁<c₂) will be described asexample 1. In this case, terminal 100 divides an SC-FDMA signal andgenerates a cluster having vector length N′=2⁰*3¹*5²=75. Here, in thecluster of vector length N′=75, column vectors having cycles of 1, 3, 5,15, 25 and 75 are partially orthogonal to each other. Therefore, thenumber of column vectors which are partially orthogonal to each other inthe cluster is 6.

On the other hand, a case with c₀=2, c₁=1, c₂=1 will be described as acase in example 2 (that is, the present embodiment). In this case,terminal 100 divides an SC-FDMA signal and generates a cluster of vectorlength N′=2²*3¹*5¹=60. Here, in the cluster of vector length N′=60,column vectors having cycles of 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30 and60 are partially orthogonal to each other. Therefore, the number ofcolumn vectors which are partially orthogonal to each other in thecluster is 12.

When example 1 is compared with example 2, in (example 2: the presentembodiment), the cluster size (N′=60) of the cluster is smaller than thecluster size (N′=75) of the cluster in example 1, but it is possible toproduce a greater number of column vectors which are partiallyorthogonal to each other in the cluster. That is, when the cluster size(here, vector length N′) increases, it is generally possible to increasethe number of column vectors of the DFT matrix which are partiallyorthogonal to each other in the cluster, whereas the present embodimentcan increase the number of combinations of column vectors which have ashorter cycle and are partially orthogonal to each other in the cluster.Thus, even when the bandwidth of the cluster is narrow (even when thelength of the cluster is short), the number of partially orthogonalvectors in the cluster can be increased. Therefore, compared to<division method 1-4> in Embodiment 1, the present embodiment canfurther reduce ISI caused by the loss of orthogonality of the DFT matrixin the cluster.

In the present invention, the division method using the relationshipbetween the base of the power (x₀<x₁<x₂< . . . <x_(M-1)) and theexponent of the power (c₀≧c₁≧₂≧ . . . ≧c_(M-1)) may be applied to allcluster sizes. When, for example, two clusters are generated from anSC-FDMA signal (spectrum) generated through DFT processing with N=420points, the terminal may divide the SC-FDMA signal after setting thecluster sizes of the two clusters to 360 and 60 respectively and map thetwo clusters to non-continuous bands. Here, since 360 and 60 can beexpressed by 360=2³*3²*5¹ and 60=2²*3¹*5¹, both cluster sizes satisfythe condition (relationship between the base of the power (x₀<x₁<x₂< . .. <x_(M-1)) and the exponent of the power (c₀≧c₁≧c₂≧ . . . ≧c_(M-1))) inthe present embodiment. This makes it possible to increase the number ofcolumn vectors of the DFT matrix having a partially orthogonalrelationship in all clusters and thereby further reduce ISI caused bythe loss of orthogonality of the DFT matrix in all non-continuouslyallocated bands.

Furthermore, in the present invention, when, for example, the base ofthe power becomes x₀<x₁< . . . <x_(M-1) and the exponent of the powerbecomes c₀≧c₁≧ . . . ≧c_(M′-1), the terminal can set vector length N′(=x₀ ^(c0)*x₁ ^(c1)* . . . *x_(M-1) ^(cM-1)<N) to minimum division unitX when generating clusters. Here, M′ is a finite number showing aninteger equal to or greater than 2. The terminal (division section 111)may generate a plurality of clusters by dividing the SC-FDMA signal witha partially orthogonal bandwidth of multiple p₀X (where p₀ is an integerequal to or greater than 1) of minimum division unit X thereof.

Thus, it is possible to create (partially) orthogonal relationships inall clusters in a vector length of minimum division unit X where agreater number of column vectors in a partially orthogonal relationshipcan be secured. Furthermore, with a cluster having a cluster size of p₀X(p₀≧2) greater than minimum division unit X, it is possible to create anumber of partially orthogonal relationships greater than the number ofcolumn vectors which have a partially orthogonal relationship in thelength of minimum division unit X between column vectors in the cluster.That is, it is possible to secure an ISI reduction effect obtained byminimum division unit X in all clusters generated by dividing theSC-FDMA signal. Furthermore, by sharing minimum division unit X betweenthe base station and the terminal in this case, only multiplier p₀ maybe reported from the base station to the terminal (or from the terminalto the base station) as control information on the division. This allowsthe amount of information required to report the control information tobe reduced.

Furthermore, when setting minimum division unit X (vector length N′)=x₀^(c0)*x₁ ^(c1)* . . . *x_(M′-1) ^(cM,-1)(<N) in generating clusters,dividing the SC-FDMA signal with multiple p₀X (where p₀ is an integerequal to or greater than 1) of minimum division unit X thereof andgenerating a plurality of clusters, the present invention may representmultiplier p₀ by a product of powers using a combination (x₀, x₁, . . ., x_(M-1)) of minimum division unit X and the same base of the power(prime number). That is, the present invention may also set multiplierp₀ represented by p₀=x₀ ^(d0)*x₁ ^(d1)**x_(M′-1) ^(dm′-1) (d₀, d₁, . . ., d_(M′-1) is an integer equal to or greater than 0, where at least oneof d₀, d₁, . . . , d_(M′-1) is an integer equal to or greater than 1).That is, the terminal (division section) divides the SC-FDMA signal witha partially orthogonal bandwidth corresponding to multiple p₀Xcalculated by multiplying minimum division unit X by multiplier p₀represented by a product (x₀ ^(d0)*x₁ ^(d1)* . . . *x_(M′-1) ^(dM′-1))of powers using a combination (x₀, x₁, . . . , x_(M′-1)) of the samebase as the combination (x₀, x₁, . . . , x_(M′-1)) of a plurality ofbases of powers constituting a product of powers (x₀ ^(c0)*x₁ ^(c1)* . .. *x_(M′-1) ^(dM′-1)) representing minimum division unit X. Whenmultiplier p₀ is set in this way, the size of a cluster generated in alength (bandwidth) p₀ times minimum division unit X can be representedby p₀X=x₀ ^((c0+d0))*x₁ ^((c1+d1))* . . . *x_(M′-1)^((c(M′-1)+d(M′-1))). That is in that cluster, it is possible toincrease the number of combinations of hierarchically partiallyorthogonal column vectors in lengths of the power of x₀, power of x₁, .. . , power of x_(M′-1). By this means, it is possible to createpartially orthogonal relationships between column vectors of the DFTmatrix in a cycle of the power of x_(i) (i=0 to M′−1) in all clustersgenerated by dividing the SC-FDMA signal and thereby further improve theISI reduction effect in a cluster having a length (bandwidth) of p₀X.

Furthermore, in the method of setting aforementioned multiplier p₀=x₀^(d0)* x₁ ^(d1)* . . . *x_(M′-1) ^(dM′-1) (d₀, d₁, . . . , d_(M′-1) isan integer equal to or greater than 0, where at least one of d₀, d₁, . .. , d_(M′-1) is an integer equal to or greater than 1) of the presentinvention, the terminal may set exponent d_(i) corresponding to aplurality of powers constituting a product of powers representingmultiplier p₀ to an equal value or a smaller value as the value of x_(i)increases for the bases of powers (x₀, x₁, . . . , x_(M′-1)) and theexponents of powers (d₀, d₁, . . . , d_(M′-1)). That is, when the baseof the power (prime number) of multiplier p₀ has a relationship ofx_(i)<x_(i′) (i≠i′), the terminal sets exponent d_(i) corresponding tobase x_(i) so as to satisfy d_(i)≧d_(i′) (i≠i′). Therefore, when thebase of the power of multiplier p₀ has a relationship of x₀<x₁<x₂< . . .<x_(M′-1), the terminal may set multiplier p₀ so that the exponents havea relationship of d₀≧d₁≧d₂≧ . . . ≧d_(M′-1). That is, the terminal(division section) divides the SC-FDMA signal with a partiallyorthogonal bandwidth corresponding to multiple p₀X calculated bymultiplying minimum division unit X by multiplier p₀ where among aplurality of powers constituting a product of powers (x₀ ^(d0)*x₁ ^(d1)*. . . *x_(M′-1) ^(dM,-1)) representing multiplier p₀, exponent valued_(i) of certain power x_(i) ^(di) becomes equal to or smaller thanexponent value d_(i′) of power X_(i′) ^(di′) having a smaller base thanbase x_(i) of certain power x_(i) ^(di) (that is, power corresponding tox_(i′)<x_(i), where i′≠i) and becomes equal to or greater than exponentvalue d_(i″) of power X_(i″) ^(di″) having a greater base than basex_(i) of certain power x_(i) ^(di) (that is, power corresponding tox_(i″)>x_(i), where i′≠i)

This allows a relationship of (c₀+d₀)≧(c₁+d₁)≧≧(c_(M′-1)+d_(M′-1)) to becreated with a cluster whose length (bandwidth) can be represented byp₀X=x₀ ^((c0+d0))*x₁ ^((c1+d1))* . . . *x_(M′-1) ^((cM′-1+dM′-1)). Thatis, in a cluster having a length (bandwidth) of p₀X, it is possible toincrease the number of combinations of column vectors which have ashorter cycle and are hierarchically partially orthogonal to each other.This makes it possible to create partially orthogonal relationshipsbetween column vectors of the DFT matrix even in a cycle of a power ofx_(i) (i=0 to M′−1) in all clusters generated by dividing an SC-FDMAsignal and thereby further reduce ISI.

FIG. 14 shows cluster size N′ assuming M=3 and minimum division unitX=12=2²*3¹*5⁰ (that is, x₀(=2)<x₁(=3)<x₂(=5), c₀(=2)≧c₁(=1)≧c₂(=0))wherein multiplier p₀=x₀ ^(d0)*x₁ ^(d1)* . . . *x_(M′-1) ^(dM′-1) has arelationship of x₀<x₁<x₂< . . . <x_(M′-1) and d₀≧d₁≧d₂≧ . . . ≧d_(M′-1)(where M′=3). FIG. 14 shows a case with M=M′ (=3) as an example, butM≠M′ may also be applicable. For example, in the case with number #3shown in FIG. 14, since multiplier p₀=6=2¹*3¹*5⁰ cluster sizeN′=p₀X=72=2³*3²*5⁰, satisfying a relationship of(c₀+d₀)(=3)≧(c₁+d₁)(=2)≧(c₂+d₂)(=0). That is, in a cluster of vectorlength N′=72, it is possible to create combinations of column vectorswhich have a shorter cycle such as 2, 3, 4, 6, 8, 9, . . . and in whichcolumn vectors of the DFT matrix are made to be hierarchically partiallyorthogonal in lengths of a power of 2, power of 3, power of 4, . . . .

Furthermore, as described in <division method 1-3> of Embodiment 1, whenthe SC-FDMA signal is divided with partially orthogonal bandwidth B′corresponding to vector length N′ which is a multiple of a prime number(N′=a₀x₀ (where the prime number is x₀, coefficient a₀ is an integerequal to or greater than 1)), that is, when the SC-FDMA signal isdivided assuming that x₀ is a minimum division unit and that the clustersize of each cluster is a length corresponding to a multiple of theminimum division unit, the multiplier (coefficient a₀) may be power x₀^(d0) of prime number x₀ (here, d₀ is an integer equal to or greaterthan 0). This makes it possible to increase the number of combinationsof column vectors which are hierarchically partially orthogonal in acycle of a power of x₀ in a cluster having a length of a₀x₀(=x₀ ^(d0+1))and thereby further reduce ISI more than <division method 1-3> ofEmbodiment 1.

Furthermore, as described in <division method 1-3> of Embodiment 1, whenthe SC-FDMA signal is divided with partially orthogonal bandwidth B′corresponding to vector length N′ which is a multiple of a product oftwo or more prime numbers (e.g. N′=b₀(x₀*x₁) (where x₀ and x₁ are primenumbers, coefficient b₀ is an integer equal to or greater than 1), thatis, when the SC-FDMA signal is divided using (x₀*x₁) as a minimumdivision unit and assuming the size of each cluster to be a lengthcorresponding to a multiple of the minimum division unit, the multiplier(coefficient b₀) may be power (x₀*x₁ ^(d0)) of a product (x₀*x₁) of theprime numbers (here, d₀ is an integer equal to or greater than 0). Thismakes it possible to increase the number of combinations of columnvectors which are hierarchically partially orthogonal in a cycle ofpowers of x₀, x₁ and (x₀*x₁) of a cluster having a length ofb₀(x₀*x₁)(=(x₀*x₁)^(d0+1)) and thereby further reduce ISI more than<division method 1-3> of Embodiment 1.

Embodiment 5

A case has been described in Embodiment 1 and Embodiment 4 where asshown in FIG. 1, the division section is connected to the DFT section ofthe terminal, the output signal (DFT output) of the DFT section isdirectly divided using the aforementioned division method and aplurality of clusters are thereby generated. By contrast, the presentembodiment will describe a case where a shifting section is providedbetween the DFT section and the division section. To be more specific,the terminal according to the present embodiment causes the shiftingsection to cyclically frequency-shift DFT output (SC-FDMA signal(spectrum)) outputted from the DFT section, divide the SC-FDMA signalafter the cyclical frequency shift among partially orthogonal bandwidths(lengths) and generate a plurality of clusters.

FIG. 15 shows a configuration of a transmitting apparatus (terminal)according to the present embodiment. In terminal 300 shown in FIG. 15,the same components as those in Embodiment 1 (FIG. 1) will be assignedthe same reference numerals and descriptions thereof will be omitted.

Shifting section 301 receives a frequency domain signal (SC-FDMA signal)generated by applying DFT processing to a time domain symbol sequencefrom DFT section 110 as input and receives an amount of shift (amount ofcyclic frequency shift) in a frequency domain set by the base station(or terminal 300) from control section 106 as input. Shifting section301 then cyclically frequency-shifts the SC-FDMA signal inputted fromDFT section 110 within a DFT band (DFT size N) in DFT processing by DFTsection 110 according to the amount of cyclic frequency shift inputtedfrom control section 106. That is, shifting section 301 applies cyclicfrequency shift to the SC-FDMA signal within the DFT band. Shiftingsection 301 may also be configured so as not to cyclicallyfrequency-shift the SC-FDMA signal (spectrum) of the pilot symbol of thesequence in which the data symbol and pilot symbol inputted to shiftingsection 301 are time-multiplexed. Shifting section 301 outputs thecyclically frequency-shifted SC-FDMA signal to division section 111.Details of the cyclic frequency shifting processing on the SC-FDMAsignal (spectrum) by shifting section 301 will be described later.

Division section 111 divides the cyclically frequency-shifted SC-FDMAsignal inputted from shifting section 301 with partially orthogonallength (vector length) N′ and generates a plurality of clusters usingone of the division methods described in the aforementioned embodiments(e.g. Embodiment 1 or Embodiment 4).

Next, FIG. 16 shows the configuration of a receiving apparatus (basestation) according to the present embodiment. Base station 400 shown inFIG. 16 determines allocation of uplink frequency resources, parameters(cluster size and number of clusters or the like) about spectraldivision at each terminal and amount of cyclic frequency shift andreports the determined information to each terminal as information to bereported. Base station 400 may also report information on frequencyresource allocation taking account of influences of spectral divisionand the amount of cyclic frequency shift based on parameters aboutspectral division to the terminal. Each terminal (terminal 300) thendivides the cyclically frequency-shifted SC-FDMA signal (spectrum) basedon parameters about spectral division included in the informationreported from base station 400.

In the configuration of receiving apparatus (base station 400) shown inFIG. 16, the configuration except reverse shifting section 408, that is,the configuration in which an output signal from combining section 407is directly inputted to IDFT section 409 corresponds to theconfiguration of the receiving apparatus (base station) (not shown) ofEmbodiment 1.

The receiving apparatus (base station 400) shown in FIG. 16 is comprisedof antenna 401, radio receiving section 402, CP removing section 403,FFT section 404, demapping section 405, FDE section 406, combiningsection 407, reverse shifting section 408, IDFT section 409,demodulation section 410, decoding section 411, measuring section 412,scheduler 413, control section 414, generation section 415, codingsection 416, modulation section 417 and radio transmitting section 418.

Radio receiving section 402 of base station 400 receives an uplinkC-SC-FDMA signal transmitted from each terminal via antenna 401 andapplies reception processing such as down-conversion, A/D conversion tothe C-SC-FDMA signal. Radio receiving section 402 outputs the C-SC-FDMAsignal subjected to the reception processing to CP removing section 403.

CP removing section 403 removes a CP added at the head of the C-SC-FDMAsignal inputted from radio receiving section 402 and outputs theC-SC-FDMA signal after the removal of the CP to FFT (Fast FourierTransform) section 404.

FFT section 404 applies FFT to the C-SC-FDMA signal after the removal ofthe CP inputted from CP removing section 403 to convert the C-SC-FDMAsignal to frequency domain C-SC-FDMA signals, that is, subcarriercomponents (orthogonal frequency components). FFT section 404 outputsthe subcarrier components after the FFT to demapping section 405.Furthermore, when a subcarrier component after the FFT is a pilotsignal, FFT section 404 outputs the subcarrier component to measuringsection 412.

Demapping section 405 demaps (extracts) a C-SC-FDMA signal (data signal)allocated to each subcarrier component (orthogonal frequency component)of a frequency resource used by a target terminal from the subcarriercomponents inputted from FFT section 404 based on frequency resourcemapping information of the terminal inputted from control section 414.Demapping section 405 then outputs the demapped C-SC-FDMA signal to FDEsection 406.

FDE section 406 calculates an FDE weight based on an estimate value of afrequency channel gain between each terminal and base station 400estimated by an estimation section (not shown) and equalizes theC-SC-FDMA signals inputted from demapping section 405 in the frequencydomain using the calculated FDE weight. FDE section 406 then outputs thesignal after the FDE to combining section 407.

Combining section 407 combines the C-SC-FDMA signals (that is, C-SC-FDMAsignals (spectra) after the FDE made up of a plurality of clusters)inputted from FDE section 406 in the frequency domain based on thecluster size and the number of clusters inputted from control section414. Combining section 407 then outputs the combined C-SC-FDMA signal toreverse shifting section 408.

Reverse shifting section 408 cyclically frequency-shifts in thedirection opposite to the direction of shifting section 301 of terminal300 (that is, reverse cyclic frequency-shifts) the combined C-SC-FDMAsignal (spectrum) after the FDE according to the amount of cyclicfrequency shift inputted from control section 414 (the same amount ofcyclic frequency shift as the amount of cyclic frequency shift used byshifting section 301 of terminal 300). When, for example, the amount ofcyclic frequency shift of shifting section 301 of terminal 300 is+z(−z), reverse shifting section 408 of base station 400 performs a−z(+z) cyclic frequency shift on the combined signal after the FDE.Reverse shifting section 408 then outputs the C-SC-FDMA signal after thereverse cyclic frequency shift to IDFT section 409.

IDFT section 409 applies IDFT processing to the C-SC-FDMA signalinputted from reverse shifting section 408 (C-SC-FDMA signal (spectrum)combined after the FDE and subjected to a reverse cyclic frequencyshift) and thereby transforms the C-SC-FDMA signal to a time domainsignal. IDFT section 409 then outputs the time domain signal todemodulation section 410.

Demodulation section 410 demodulates the time domain signal inputtedfrom IDFT section 409 based on MCS information (modulation scheme)inputted from scheduler 413 and outputs the demodulated signal todecoding section 411.

Decoding section 411 decodes the signal inputted from demodulationsection 410 based on MCS information (coding rate) inputted fromscheduler 413 and outputs the decoded signal as a received bit sequence.

On the other hand, measuring section 412 measures channel quality ofeach terminal in the frequency domain, for example, SINR(Signal-to-Interference plus Noise power Ratio) for each subcarrier ofeach terminal using pilot signals (pilot signals transmitted from eachterminal) included in subcarrier components inputted from FFT section404 and thereby generates channel quality information (CQI) of eachterminal. Measuring section 412 then outputs the CQI of each terminal toscheduler 413.

Scheduler 413 calculates priority of allocation of uplink sharedfrequency resources (PUSCH: Physical Uplink Shared CHannel) to eachterminal using inputted information on QoS (Quality of Service) or thelike of each terminal. Scheduler 413 then allocates each subcarrier (orfrequency resource block RB (Resource Block) made up of a plurality ofsubcarriers) to each terminal using the calculated priority and the CQIinputted from measuring section 412. PF (Proportional Fairness) or thelike may be used as an algorithm used to allocate frequency resources.Furthermore, scheduler 413 outputs frequency resource allocationinformation of each terminal showing frequency resources of eachterminal allocated using the above described method to control section414 and generation section 415 and outputs control information (MCSinformation or the like) other than the frequency resource allocationinformation to demodulation section 410, decoding section 411 andgeneration section 415.

Control section 414 calculates the number of clusters and the clustersize of the terminal using the frequency resource allocation informationof each terminal inputted from scheduler 413, category information ofthe terminal (information including the DFT size) and partiallyorthogonal condition information (information showing partiallyorthogonal condition (equation 1 or 2) of C-SC-FDMA). Furthermore,control section 414 calculates frequency resources to which C-SC-FDMAsignals of each terminal are mapped based on the calculated number ofclusters and cluster size. Control section 414 then outputs thecalculated number of clusters and cluster size to combining section 407and outputs the frequency resource mapping information showing frequencyresources to which the C-SC-FDMA signals of each terminal are mapped todemapping section 405. Furthermore, control section 414 sets an amountof cyclic frequency shift used in reverse shifting section 408 andshifting section 301 of terminal 300 and outputs information on the setamount of cyclic frequency shift to reverse shifting section 408 andgeneration section 415.

Generation section 415 converts the frequency resource allocationinformation inputted from scheduler 413, control information (MCSinformation or the like) other than the frequency resource allocationinformation and information on the amount of cyclic frequency shiftinputted from control section 414 to a binary control bit sequence to bereported to each terminal and thereby generates a control signal.Generation section 415 then outputs the generated control signal tocoding section 416.

Coding section 416 codes the control signal inputted from generationsection 415 and outputs the coded control signal to modulation section417.

Modulation section 417 modulates the control signal inputted from codingsection 416 and outputs the modulated control signal to radiotransmitting section 418.

Radio transmitting section 418 applies transmission processing such asD/A conversion, amplification and up-conversion to the control signalinputted from modulation section 417 and transmits the signal subjectedto the transmission processing to each terminal via antenna 401.

Next, details of cyclic frequency shifting processing on an SC-FDMAsignal (spectrum) by shifting section 301 of terminal 300 will bedescribed.

Since C-SC-FDMA performs precoding using a DFT matrix, even if DFToutput (output signal of DFT processing) is cyclically shifted within aDFT band (DFT size N), it is possible to create a partially orthogonalrelationship among column vectors at an arbitrary position of the DFToutput as long as the cluster size of clusters generated throughdivision is length N′ that satisfies equation 1. The present embodimenttakes advantage of this feature.

This will be described more specifically below. That is, a feature in asection where column vectors of the DFT matrix are partially orthogonalto each other will be described.

First, partially orthogonal conditions among column vectors of the DFTmatrix in a segment of k=0 to N′−1 of vector length N (section: k=0 toN−1) will be described.

Two column vectors f_(i)(k)(=f_(i)) and f_(i)′ (k)(=f_(i′)) (where i′≠i)having different angular frequencies in the DFT matrix are defined asfollowing equation 3.

[3] $\begin{matrix}\left\{ {{\begin{matrix}{{f_{i}(k)} = {\frac{1}{\sqrt{N}}^{{- j}\; 2\pi \; \frac{i}{N}k}}} \\{{f_{i^{\prime}}(k)} = {\frac{1}{\sqrt{N}}^{{- j}\; 2\pi \; \frac{i^{\prime}}{N}k}}}\end{matrix}{for}\mspace{14mu} k} = {0 \sim {N - 1}}} \right. & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

In equation 3, N represents a DFT size (the number of DFT points) and i,i′=0 to N−1. Here, of vector length N (section: k=0 to N−1), an innerproduct (partial cross correlation without time difference) of f_(i)(k)and f_(i)′ (k) in partial vector length N′ (segment: k=0 to N′−1) is asshown in following equation 4 (where N′<N).

[4] $\begin{matrix}{{\sum\limits_{k = 0}^{N^{\prime} - 1}\; {{f_{i}(k)}{f_{i^{\prime}}^{*}(k)}}} = {{\frac{1}{N}{\sum\limits_{i = 0}^{N^{\prime} - 1}\; ^{{- j}\; 2\pi \; \frac{i - 1^{\prime}}{N}k}}} = {\frac{1}{N}^{{- j}\; \pi \; \frac{i - i^{\prime}}{N}{({N^{\prime} - 1})}}\frac{\sin \left( {\pi \frac{i - i^{\prime}}{N}N^{\prime}} \right)}{\sin \; \left( {\pi \frac{i - i^{\prime}}{N}} \right)}}}} & \left( {{Equation}\mspace{14mu} 4} \right)\end{matrix}$

Superscript * in equation 4 represents a complex conjugate. It is clearfrom equation 4 that two orthogonal column vectors, that is, two columnvectors partially orthogonal at partial vector length N′ (segment: k=0to N′−1) are a combination of column vectors where exp(−j2π(i-i′)k/N) ofangular frequency 2π(i-i′)/N in segment k=0 to N′−1 rotates at least oneround. That is, when (i-i′)N′/N is an integer where two column vectorsf_(i)(k) and f_(i)′ (k) are partially orthogonal to each other in asection of k=0 to N′−1. Therefore, a specific relationship as shown inequation 5 below exists between vector length N′ (<N) in which arbitrarytwo different column vectors f_(i)(k) and f_(i′)(k) (where i′≠i) of theplurality of column vectors constituting a DFT matrix are partiallyorthogonal to each other and DFT size (column vector length) N of theDFT matrix.

[5] $\begin{matrix}{N^{\prime} = {{{\frac{I}{i - i^{\prime}}}N} = {\frac{I}{{i - i^{\prime}}}N}}} & \left( {{Equation}\mspace{14mu} 5} \right)\end{matrix}$

Here, I is a non-zero integer that satisfies |I|<|i-i′|. That is, whenthe cluster size is expressed by length N′ of equation 5 (or equation1), it is possible to create a partially orthogonal relationship betweencolumn vectors of DFT in the cluster.

Next, partially orthogonal conditions between column vectors of the DFTmatrix in a segment of k=z to z+N′−1 of vector length N (section: k=0 toN−1) will be described. Reference character z is an arbitrary realnumber.

From equation 3, an inner product of f_(i)(k) and f_(i′)(k) in partialvector length N′ (segment: k=z to z+N′−1) of vector length N (section:k=0 to N−1) is as shown in following equation 6) (where N′<N).

[6] $\begin{matrix}{{{\sum\limits_{k = z}^{z + N^{\prime} - 1}\; {{f_{i}(k)}{f_{i^{\prime}}^{*}(k)}}} = {{\frac{1}{N}{\sum\limits_{i = z}^{z + N^{\prime} - 1}\; ^{{- j}\; \pi \frac{i + i^{\prime}}{N}k}}} = {\frac{1}{N}^{{- j}\; \pi \frac{i - i^{\prime}}{N}{({{2z} + N^{\prime} - 1})}}\frac{\sin \left( {\pi \frac{i - i^{\prime}}{N}N^{\prime}} \right)}{\sin \left( {\pi \frac{i - i^{\prime}}{N}} \right)}}}}{{Equation}\mspace{14mu} {{\overset{\prime}{4}}^{\;}\mspace{11mu}}^{\text{?}\frac{{- i} - i^{\prime}}{\square}}\text{?}}{\text{?}\text{indicates text missing or illegible when filed}}} & \left( {{Equation}\mspace{14mu} 6} \right)\end{matrix}$

In equation 6, superscript * denotes a complex conjugate. From equation6, since (1/N)exp(−jπ(i-i′)(2z)/N)≠0, in order for equation 6 to be 0requires equation 4 to be 0. Therefore, it is understandable that thecondition for column vectors of the DFT matrix to be partiallyorthogonal to each other in segment k=z to z+N′−1 is also the same asequation 1 described in Embodiment 1 or equation 5 above (partiallyorthogonal condition in segment k=0 to N′−1).

That is, it is understandable that there is a feature that a partiallyorthogonal relationship can be created between column vectors atpositions (positions of the band) of an arbitrary spectrum of theSC-FDMA signal (spectrum) which is the DFT output as long as the length(bandwidth) of clusters generated by dividing the SC-FDMA signalsatisfies the condition of the partially orthogonal vector length N′(bandwidth B′) of equation 1 or equation 2 (equation 5). Furthermore,length N′ thereof may be cyclic within the DFT band. That is, if onlythe length (bandwidth) of the cluster satisfies length N′, the partiallyorthogonal relationship between column vectors of the DFT matrix can bemaintained, and therefore terminal 300 may apply a cyclic frequencyshift to the DFT output in the DFT band.

FIG. 17A and FIG. 17B show a case where a segment of vector length N′=8is set when DFT size (the number of points) N=10 (DFT output numbers 0to 9). Furthermore, in FIG. 17A, a segment of length N′=8 is set to DFToutput numbers 0 to 7 (that is, amount of cyclic frequency shift z=0),while in FIG. 17B, a segment of length N′=8 is set to DFT output numbers3 to 9 and 0 (that is, z=3) cyclically shifted within the DFT band.Here, when length N′ (=8) of the segment satisfies equation 1 (orequation 5), a partially orthogonal relationship can be created betweencolumn vectors within the band of DFT output numbers 0 to 7 in FIG. 17Aand a partially orthogonal relationship can be created between columnvectors within the band of DFT output numbers 3 to 9 and 0 in FIG. 17B.

Taking advantage of the above described feature, shifting section 301 ofterminal 300 cyclically frequency-shifts the SC-FDMA signal which is theDFT output inputted from DFT section 110 by z points within the DFTband. Division section 111 then divides the SC-FDMA signal after thecyclic frequency shift with a partially orthogonal bandwidth using oneof the division methods described in Embodiment 1 or Embodiment 3, andthereby generates a plurality of clusters.

Here, FIGS. 18A to C show a series of processing steps in shiftingsection 301 and division section 111. In FIGS. 18A to C, assuming DFTsize N=72 points (DFT output numbers 0 to 71), terminal 300 generatestwo clusters (cluster #0 and cluster #1). Furthermore, here, shiftingsection 301 cyclically shifts the DFT output from low to highfrequencies. Furthermore, FIG. 18A shows 72-point DFT output (SC-FDMAsignals) obtained after DFT section 110 performs DFT processing on atime domain symbol sequence.

Shifting section 301 applies a cyclic frequency shift with z=4(subcarriers) to the DFT output shown in FIG. 18A within the DFT band ofN=72 points. Thus, a signal as shown in FIG. 18B in which DFT outputnumbers 0 to 71 are cyclically shifted by z=4 in a direction from low tohigh frequencies (that is, DFT output numbers 68 to 71, 0 to 67) isobtained.

As shown in FIG. 18C, division section 111 then divides the signal of 72points (DFT output numbers 68 to 71, 0 to 67) after the cyclic frequencyshift by z=4 (subcarriers) shown in FIG. 18B into two clusters; cluster#0 (DFT output numbers 68 to 71, 0 to 7) having a partially orthogonalbandwidth (vector length N′=12) and cluster #1 (DFT output numbers 8 to67) having a partially orthogonal bandwidth (vector length N′=60).Mapping section 112 then maps cluster #0 and cluster #1 shown in FIG.18C to non-continuous frequency bands and thereby obtains C-SC-FDMAsignals.

By this means, the present embodiment can improve flexibility of mappingof DFT output on frequency resources (subcarriers) while making columnvectors of the DFT matrix partially orthogonal to each other withinclusters. When, for example, there is always an interference signal withhigh power in specific frequency resources, the terminal may cyclicallyfrequency-shift the DFT output before dividing the DFT output (SC-FDMAsignal). Thus, by maintaining a partially orthogonal relationship inclusters, it is possible to prevent the DFT output mapped to specificresources from always receiving large interference while reducing ISI.That is, according to the present embodiment, the terminal can performinterference preventing control without changing positions of frequencyresources allocated to the SC-FDMA signal.

In the present invention, the direction of a cyclic frequency shift maybe a direction from low to high frequencies or a direction from high tolow frequencies. That is, the value of cyclic frequency shift z may beplus (+) or minus (−).

Furthermore, a configuration of terminal 300 as shown in FIG. 15 hasbeen described in the present embodiment in which the DFTsection→shifting section→division section→mapping section are connectedin that order. However, the terminal according to the present inventionmay also have a configuration (not shown) in which the DFTsection→division section→shifting section→mapping section are connectedin that order. In this case, the terminal may cyclically frequency-shifta plurality of subcarrier components belonging to each cluster over aplurality of clusters (a plurality of clusters after division notsubjected to any cyclic frequency shift) and perform mapping similar tothat in FIG. 18C on the plurality of clusters. By this means, even whenthe connection order of components of the terminal is changed, effectssimilar to those of the present embodiment can be obtained.

Furthermore, with regard to Fourier transform, instead of theconfiguration (FIG. 15) of realizing a frequency domain cyclic frequencyshift described in the present embodiment, the terminal may also adopt aconfiguration of multiplying the time domain signal outputted from theIFFT section by phase rotation (and amplitude component) correspondingto a cyclic frequency shift in the frequency domain. That is, instead ofthe shifting section of the terminal shown in FIG. 15, a configuration(not shown) may also be adopted in which a multiplication section thatmultiplies the time domain signal outputted from the IFFT section byphase rotation (and amplitude component) corresponding to a cyclicfrequency shift in the frequency domain is connected after the IFFTsection. Effects similar to those of the present embodiment can beobtained in this case, too.

Furthermore, a configuration the base station as shown in FIG. 16 hasbeen described in the present embodiment in which the demappingsection→FDE section→combining section→reverse shifting section→IDFTsection are connected in that order. However, the base station accordingto the present invention may also have a configuration (not shown) inwhich the demapping section→reverse shifting section→FDEsection→combining section→IDFT section are connected in that order ordemapping section→FDE section→reverse shifting section→combiningsection→IDFT section are connected in that order. In the case of theconfiguration, for example, in order of the demapping section→reverseshifting section→FDE section→combining section→IDFT section, the basestation may cause the reverse shifting section to perform a reversecyclic frequency shift on the demapped signal sequence, cause the FDEsection to also perform a reverse cyclic frequency shift on the FDEweight and perform FDE on the demapped signal sequence after the reversecyclic frequency shift using the FDE weight after the reverse cyclicfrequency shift. On the other hand, in the case of the configuration inorder of the demapping section→FDE section→reverse shiftingsection→combining section→IDFT section, the base station may cause thereverse shifting section to perform a reverse cyclic frequency shift onthe signal sequence after the FDE and cause the combining section tocombine a plurality of clusters after the reverse cyclic frequency shiftmapped to non-continuous frequency bands. Even when the connection orderof components of the base station is changed in this way, effectssimilar to those of the present embodiment can be obtained.

Furthermore, with regard to Fourier transform, instead of theconfiguration (FIG. 16) of performing reverse cyclic frequency shiftingin the frequency domain described in the present embodiment, aconfiguration may also be adopted in which the time domain signaloutputted from the IDFT section of the base station may be multiplied byphase rotation (and amplitude component) corresponding to the reversecyclic frequency shift in the frequency domain. That is, a configuration(not shown) may also be adopted in which instead of the reverse shiftingsection shown in FIG. 16, a multiplication section that multiplies thetime domain signal outputted from the IDFT section by phase rotation(and amplitude component) corresponding to the reverse cyclic frequencyshift in the frequency domain is connected after the IDFT section.Effects similar to those of the present embodiment can be obtained inthis case, too.

Furthermore, in the present invention, when the terminal transmitsC-SC-FDMA signals in parallel in the frequency domain, the terminal mayprovide a plurality of units made up of a coding section, modulationsection, multiplexing section, DFT section, shifting section anddivision section as shown in FIG. 19. The terminal may individually setthe amount of shift in each unit and apply a cyclic frequency shift tothe DFT output of each unit. In terminal 500 shown in FIG. 19, M units501-1 to 501-M are configured and each unit is individually providedwith a coding section, a modulation section, a multiplexing section, aDFT section, a shifting section and a division section for atransmission bit sequence, and a case where M C-SC-FDMA signals aretransmitted in parallel in the frequency domain is shown. By adoptingthe configuration shown in FIG. 19, in a radio channel having differentradio wave propagation environments in different frequency bands such asa wideband radio channel configured of many multi-paths and havingfrequency selectivity, it is possible to improve flexibility of mappingof signals in each unit on frequency resources (subcarriers) by applyingan individual cyclic frequency shift to each unit while making columnvectors of the DFT matrix partially orthogonal to each other in eachcluster of a C-SC-FDMA signal generated in each unit.

The amount of cyclic frequency shift may be shared among a plurality ofunits and control information on one common amount of cyclic frequencyshift may be reported from the base station to the terminal (or from theterminal to the base station). Furthermore, the amount of individualcyclic frequency shift per unit may be set to the same value and controlinformation on the amount of cyclic frequency shift of each unit may bereported from the base station to the terminal (or from the terminal tothe base station) at the same time. When, for example, the sametransmission format (e.g. the same MCS set or the same C-SC-FDMAdivision method (the number of clusters or cluster size or the like)) isused among a plurality of units, there is a correlation in requiredcommunication quality (e.g. SINR required to satisfy a certain errorrate) between units. Therefore, sharing the amount of cyclic frequencyshift (that is, setting the same amount of cyclic frequency shift) amonga plurality of units can further improve a correlation in requiredcommunication quality between units and control transmission formats ofthe plurality of units at the same time and reliably. Furthermore, whenone common amount of cyclic frequency shift is used, the amount ofinformation require to report from the base station to the terminal (orfrom the terminal to the base station) can be reduced.

When, for example, a bundling technique is used whereby one ACK(acknowledgment) signal is fed back when the base station normallyreceives all transmission bit sequences (transport blocks) of theplurality of units or one NACK (negative acknowledgment) signal is fedback when even one error is detected by the base station from theplurality of transport blocks from the base station to the terminal, theabove described amount of cyclic frequency shift setting method (methodof setting the same amount of cyclic frequency shift among the pluralityof units) may be used. That is, by setting the same amount of cyclicfrequency shift among a plurality of units (that is, using the samesetting method on cyclic frequency shifts), it is possible to correlatetransport blocks of the plurality of units and their respective errorproducing mechanisms. Therefore, it is possible to reduce theprobability that error-producing transport blocks and error-freetransport blocks may be mixed among transport blocks of the plurality ofunits and reduce unnecessary retransmissions of transport blocksnormally received by the base station.

Furthermore, the value of the amount of cyclic frequency shift zcorresponding to the DFT output outputted from the DFT section of theterminal in the present invention may also be set to the same value asthe length that satisfies the partially orthogonal vector length(bandwidth) corresponding to one of the division methods described inEmbodiment 1 or Embodiment 4. Thus, partially orthogonal conditionssimilar to the partially orthogonal conditions for an SC-FDMA signal(spectrum) before a cyclic frequency shift are also applicable to anSC-FDMA signal (spectrum) after a cyclic frequency shift.

Furthermore, in the present invention, amount of cyclic frequency shiftz may also be associated with a minimum division unit when dividing theSC-FDMA signal (spectrum). When, for example, the minimum division unitof the SC-FDMA signal (spectrum) is defined as N_(min), the minimumamount of shift of amount of cyclic frequency shift z may likewise beassumed to be N_(min). In this case, minimum amount of shift N_(min) maybe shared between transmitting and receiving apparatuses (terminal andbase station) and multiple kN_(min) (k is an integer) of the minimumamount of shift may be defined as amount of cyclic frequency shift zgiven to the DFT output. Thus, only multiplier (coefficient) k may benecessary as the control information on amount of cyclic frequency shiftz reported from the base station to the terminal (or from the terminalto the base station). Furthermore, when control information (multiplierk) on amount of cyclic frequency shift z is reported, amount of cyclicfrequency shift k may also be reported together with cluster divisioninformation (number of fractions or the like) or frequency resourceallocation information. This allows the amount of information requiredto report the amount of cyclic frequency shift to be reduced.

Furthermore, when C-SC-FDMA signals to which the terminal applies acyclic frequency shift are transmitted in parallel in the frequencydomain, the amount of cyclic frequency shift may be relatively definedamong C-SC-FDMA signals transmitted in parallel (e.g. among units 501-1to 501-M of terminal 500 shown in FIG. 19). To be more specific, thedifference between the amount of cyclic frequency shift of a C-SC-FDMAsignal to be a reference and the amounts of cyclic frequency shift ofother C-SC-FDMA signals may be defined as a relative amount of shift(differential amount of shift) and the relative amount of shift(differential amount of shift) may be reported from the base station tothe terminal (or from the terminal to the base station). For example, acase will be described where an amount of cyclic frequency shift of aC-SC-FDMA signal mapped to a low frequency band is set to z₀=5 and anamount of cyclic frequency shift of a C-SC-FDMA signal mapped to a highfrequency band is set to z₁=10. In this case, the difference (relativevalue)=z₁-z₀=5 between the amount of cyclic frequency shift of theC-SC-FDMA signal mapped to the low frequency band and the amount ofcyclic frequency shift of the C-SC-FDMA signal mapped to the highfrequency band may be reported together with amount of cyclic frequencyshift z₀=5 of the C-SC-FDMA signal mapped to the low frequency band tobe a reference as control information on the amount of cyclic frequencyshift to be reported from the base station to the terminal (or from theterminal to the base station). This allows overhead of the amount ofinformation required to report the amount of cyclic frequency shift tobe reduced compared to the case where the amount of cyclic frequencyshift for each C-SC-FDMA signal is reported individually. Although acase has been described here where amounts of cyclic frequency shiftcorresponding to two C-SC-FDMA signals are reported, the number ofC-SC-FDMA signals to be transmitted in parallel is not limited to 2 butmay be 3 or more.

Embodiment 6

According to the present embodiment, a terminal that performs MIMOtransmission applies individual cyclic frequency shifts within a DFTband to SC-FDMA signals transmitted to different space resources(layers, antennas or streams) to which a plurality of codewords aremapped for every different space resource. The terminal then divides thesignal of each space resource (layer, antenna or stream) with apartially orthogonal bandwidth (bandwidth corresponding to partiallyorthogonal vector length).

FIG. 20 shows a configuration of the transmitting apparatus (terminal)according to the present embodiment. In terminal 600 shown in FIG. 20,the same components as those of Embodiment 2 (FIG. 9) will be assignedthe same reference numerals and descriptions thereof will be omitted.Furthermore, terminal 600 shown in FIG. 20 is provided with two antennasthat transmit C-SC-FDMA signals using two space resources as in the caseof Embodiment 2. Terminal 600 shown in FIG. 20 differs from terminal 200(FIG. 9) in Embodiment 2 in that C-SC-FDMA processing section 601 thatgenerates an SC-FDMA signal (spectrum) transmitted through each spaceresource is individually provided with a shifting section 301 for eachbit sequence (codeword) transmitted in parallel using space resourcesafter DFT section 110.

In terminal 600 shown in FIG. 20, control section 106 outputs anindividual amount of cyclic frequency shift corresponding to eachC-SC-FDMA processing section 601 to each shifting section 301. There canbe a case where an individual amount of cyclic frequency shift forC-SC-FDMA processing section 601 may be determined by the base stationand the determined amount of cyclic frequency shift may be reported fromthe base station to the terminal or a case where the terminal maydetermine the amount of cyclic frequency shift and the determined amountof cyclic frequency shift may be reported from the terminal to the basestation.

C-SC-FDMA processing sections 601-1 and 601-2 apply processing similarto that of coding section 107 to DFT section 110 of Embodiment 2 toinputted codewords (transmission bit sequences) and thereby generateSC-FDMA signals (spectra). Each DFT section 110 of C-SC-FDMA processingsections 601-1 and 601-2 outputs the generated SC-FDMA signal (spectrum)to each shifting section 301.

Shifting section 301 applies an individual cyclic frequency shift to theSC-FDMA signal (spectrum) inputted from DFT section 110 for eachC-SC-FDMA processing section according to a codeword-specific (that is,for each C-SC-FDMA processing section) amount of cyclic frequency shiftinputted from control section 106 in the same way as in Embodiment 5.Shifting section 301 then outputs the SC-FDMA signal (spectrum) afterthe cyclic frequency shift to division section 111.

Division section 111 divides the SC-FDMA signal (spectrum) after thecyclic frequency shift inputted from shifting section 301 with apartially orthogonal bandwidth using one of the division methodsdescribed in the above described embodiments (e.g. Embodiment 1 orEmbodiment 4) and generates a plurality of clusters. Division section111 of each C-SC-FDMA processing section 601 then outputs the pluralityof clusters generated to precoding section 202.

Next, details of C-SC-FDMA processing in C-SC-FDMA processing section601 of terminal 600 will be described.

A case will be described below where as shown in FIGS. 21A to C,terminal 600 maps two codewords (codeword #0 and codeword #1) to twodifferent space resources (here, these may be layer #0 and layer #1 orantenna, streams). Furthermore, in FIGS. 21A to C, assuming DFT sizeN=72 points (DFT output numbers 0 to 71), terminal 600 generates twoclusters (cluster #0 and cluster #1). Furthermore, shifting section 301cyclically shifts the DFT output from low to high frequencies.

FIG. 21A shows 72-point DFT output (SC-FDMA signal) obtained after eachDFT section 110 of C-SC-FDMA processing sections 601-1 and 601-2performs DFT processing on two codewords #0 and #1 respectively.

Each shifting section 301 of C-SC-FDMA processing sections 601-1 and601-2 individually applies a cyclic frequency shift within the DFT band(DFT size N=72 points) to two SC-FDMA signals respectively (signal ofcodeword #0 and signal of codeword #1) shown in FIG. 21A. To be morespecific, as shown in FIG. 21B, shifting section 301 of C-SC-FDMAprocessing section 601-1 applies a cyclic frequency shift with z=0(without cyclic frequency shift) to the signal of codeword #0transmitted through layer #0 (space resource #0). Furthermore, as shownin FIG. 21B, shifting section 301 of C-SC-FDMA processing section 601-2applies a cyclic frequency shift with z=12 (with a cyclic frequencyshift) to the signal of codeword #1 transmitted through layer #1 (spaceresource #1). That is, shifting section 301 applies a cyclic frequencyshift to codewords (SC-FDMA signals) transmitted through a plurality oflayers (space resources) within the DFT band for each of the pluralityof space resources (layer, antenna or streams).

As shown in FIG. 21C, each division section 111 of C-SC-FDMA processingsections 601-1 and 601-2 divides the codeword (SC-FDMA signal) after thecyclic frequency shift into cluster #0 of vector length N′=12 andcluster #1 of vector length N′=60 and thereby generates two clusters.

By this means, in MIMO transmission, the present embodiment can flexiblyperform frequency mapping adapted to the quality of each channel (link)of space resources (layer, antenna or stream) through which codewordsare transmitted while maintaining a partially orthogonal relationshipwithin the cluster of the codewords transmitted through each spaceresource, for each codeword (each space resource, each layer, eachantenna or each stream or the like).

The present embodiment has described SU-MIMO in which transmitting andreceiving apparatuses (terminal and base station) realize MIMOtransmission using a plurality of antennas as an example. However, thepresent invention is also applicable to uplink and downlink MU-MIMO. Forexample, in downlink MU-MIMO transmission, different codewords mapped todifferent space resources (layers, antennas or streams) are codewordsdirected to different terminals. In this case, it is necessary tosatisfy required quality that differs from one receiving apparatus(terminal) to another. For example, in the case of a cellular systemsuch as mobile phone, communication quality of a terminal (receivingapparatus) located in a different place differs in great deal. Asdescribed above, according to the present embodiment, however, thetransmitting apparatus (base station) applies an individual cyclicfrequency shift to each codeword transmitted through each of spaceresources to which a plurality of codewords are mapped in differentspace resources (layers, antennas or streams). Thus, in the cluster ofeach codeword, it is possible to flexibly perform frequency mapping(cyclic frequency shift) adapted to the quality of each channel (link)of a space resource through which the codeword is transmitted for eachcodeword (each space resource, each layer, each antenna or each stream)while maintaining the partially orthogonal relationship within a clusterof each codeword.

A case has been described in the present embodiment where thetransmitting apparatus (terminal) maps two codewords to two spaceresources (layers, antennas or streams) respectively. However, in thepresent invention, the transmitting apparatus (terminal) may also applythree or more codewords to three or more space resources (layers,antennas or streams).

Furthermore, in the present invention, amount of cyclic frequency shiftz_(i) individually set for each codeword (each layer, each antenna oreach stream) may be associated with a minimum division unit whendividing an SC-FDMA signal (spectrum). When, for example, the minimumdivision unit of the SC-FDMA signal (spectrum) is defined as N_(min),the minimum amount of shift of individual amount of cyclic frequencyshift z_(i) set for each codeword (each space resource, each layer oreach stream) may also be likewise defined as N_(min). Thus, it ispossible to apply a partially orthogonal condition similar to thepartially orthogonal condition corresponding to an SC-FDMA signal(spectrum) before a cyclic frequency shift to all clusters after thecyclic frequency shift.

Furthermore, in the present invention, amount of cyclic frequency shiftz_(i) individually set for each codeword (each layer, each antenna oreach stream) may be set to a multiple of the cluster size having aminimum partially orthogonal bandwidth of the plurality of clustersgenerated by dividing the SC-FDMA signal. That is, amount of cyclicfrequency shift z_(i) may be associated with the bandwidth of thecluster having the minimum partially orthogonal bandwidth. When, forexample, the cluster size having the minimum partially orthogonalbandwidth in a certain space resource (layer, antenna or stream) isassumed to be B_(min), the amount of cyclic frequency shift in the spaceresource or another space resource may be set as kB_(min) (k is aninteger). This makes it possible to maintain an (partially) orthogonalrelationship in the frequency domain between space resources (layers,antennas or streams) and at the same time reduce interference fromdifferent clusters of different space resources.

Furthermore, a case has been described in the present embodiment wherean amount of cyclic frequency shift individually set for each codeword(each space resource, each layer, each antenna or each stream) is used.However, in the present invention, the amount of cyclic frequency shiftindividually set in each codeword (each space resource, each layer, eachantenna or each stream) may also be relatively defined between codewords(between space resources, between layers, between antennas or betweenstreams). To be more specific, a difference between the amount of cyclicfrequency shift of a reference codeword (space resource, layer, antennaor stream) and the amount of cyclic frequency shift of another codeword(space resource, layer, antenna or stream) may be defined as a relativeamount of shift (differential amount of shift) and the relative amountof shift (differential amount of shift) may be reported from the basestation to the terminal (or from the terminal to the base station). Forexample, a case where the amount of cyclic frequency shift of codeword#0 is set to z₀=5 and the amount of cyclic frequency shift of codeword#1 is set to z₁=10 will be described. In this case, a difference(relative value)=z₁-z₀=5 between the amount of cyclic frequency shift ofcodeword #0 and the amount of cyclic frequency shift of codeword #1 maybe reported together with amount of cyclic frequency shift z₀=5 ofcodeword #0 which serves as a reference, as control information on theamount of cyclic frequency shift to be reported from the base station tothe terminal (or from the terminal to the base station). Thus, overheadof the amount of information required to report the amount of cyclicfrequency shift may be reduced compared to a case where the amount ofcyclic frequency shift of each codeword (space resource, layer, antennaor stream) is individually reported. Although a case has been describedhere where the amounts of cyclic frequency shift corresponding to twocodewords are reported respectively, the number of codewords is notlimited to 2, but may be 3 or more. Furthermore, a relative value(difference value) of amount of cyclic frequency shift between resourcesindicating space resources such as layer, antenna or stream may also beused instead of codewords.

A case has been described in the present embodiment where individualamounts of cyclic frequency shifts set for each codeword (spaceresource, layer, antenna or stream) are used. However, in the presentinvention, the amount of cyclic frequency shift may be shared among aplurality of codewords (space resources, layers, antennas or streams) sothat one common amount of cyclic frequency shift may be used.Furthermore, the same amount of cyclic frequency shift may also be setamong a plurality of codewords (space resources, layers, antennas orstreams). When, for example, the transmitting apparatus (terminal) mapscodewords having the same MCS to a plurality of codewords (spaceresources, layers, antennas or streams), the amount of cyclic frequencyshift of each codeword (space resource, layer, antenna or stream) may beset to the same value (or using one common cyclic frequency shift) andthe amount of cyclic frequency shift may be reported from the basestation to the terminal (or from the terminal to the base station).Thus, codewords having substantially the same required quality mapped toa plurality of space resources (layers, antennas or streams) can becontrolled at the same time and reliably. Furthermore, when one commonamount of cyclic frequency shift is used, the amount of informationrequired to report the amount of cyclic frequency shift from the basestation to the terminal (or, from the terminal to the base station) canfurther be reduced.

Furthermore, Embodiment 2 has described the precoding method in MIMOtransmission of dividing an SC-FDMA signal of each stream with apartially orthogonal bandwidth and multiplying signals mapped tofrequency bands having the same partially orthogonal bandwidth (length)in the plurality of streams by the same spatial precoding matrixrespectively. Thus, the present embodiment may also adopt aconfiguration in which the transmitting apparatus (terminal) cyclicallyfrequency-shifts an SC-FDMA signal, then divides the SC-FDMA signal andmultiplies signals of a plurality of space resources (layers, antennasor streams) mapped to frequency bands having the same partiallyorthogonal bandwidth (length) by the same spatial precoding matrixrespectively. That is, the terminal according to the present inventionmay adopt a configuration combining Embodiment 2 and the presentembodiment. This makes it possible to obtain effects similar to therespective effects of Embodiment 2 and the present embodiment.

Furthermore, a case has been described in the present embodiment wherewhen the transmitting apparatus (terminal) transmits a plurality ofcodewords through a plurality of layers, one codeword is mapped to onespace resource (layer) (that is, a codeword and a space resource (layer)have a one-to-one correspondence). However, the present invention isalso applicable to a case where the transmitting apparatus (terminal)maps one codeword to a plurality of space resources (layers) (e.g.single codeword transmission of MIMO). For example, a case will bedescribed where the terminal performs spatial multiplexing transmissionon two codewords (codeword #0 and codeword #1) using four spaceresources (layer #0 to #3). In this case, the terminal may map a signal(modulated signal) of codeword #0 to two layers of layer #0 and layer #1and map a signal (modulated signal) of codeword #1 to two layer of layer#2 and layer #3. In this case, the terminal may apply an individualcyclic frequency shift to each codeword using an amount of cyclicfrequency shift individually set for each layer (space resource).

Furthermore, in the present invention, when mapping one codeword to aplurality of layers, the terminal may use the same amount of cyclicfrequency shift among a plurality of layers (space resources) to whichone codeword is mapped. For example, as shown in FIGS. 22A to C, a casewill be described where the terminal performs spatial multiplexingtransmission on two codewords (codeword #0 and codeword #1) using fourlayers (layers #0 to #3). In FIG. 22A, the terminal maps each codewordto two layers (space resources). Furthermore, as shown in FIG. 22B, theterminal sets the same amount of cyclic frequency shift between layers(space resources) to which the same codeword is mapped. For example, asshown in FIG. 22B, the terminal maps the signal of codeword #0 to twolayers (space resources) of layer #0 and layer #1 and uses the sameamount of cyclic frequency shift z₀=12 in two layers (layer #0 and layer#1). Likewise, as shown in FIG. 22B, the terminal maps the signal ofcodeword #1 to two layers (space resources) of layer #2 and layer #3 anduses the same amount of cyclic frequency shift z₁=60 in the two layers(layer #2 and layer #3). As shown in FIG. 22C, the terminal divides thesignal after a cyclic frequency shift into two clusters (cluster #0 andcluster #1) having partially orthogonal bandwidths. Thus, sincedifferent modulated signals included in the same codeword mapped todifferent space resources (layers) are subjected to a cyclic frequencyshift using the same amount of cyclic frequency shift, it is possible toequalize an apparent channel variation caused by the cyclic frequencyshift among the same codewords mapped to different space resources(layers). Thus, it is possible to make a likelihood distribution of bitsor symbols within the codeword uniform and reliably perform adaptivecontrol such as adaptive modulation.

A case has been described above (e.g. FIG. 22) where the same amount ofcyclic frequency shift is applied within the codewords mapped todifferent space resources (layers). However, the present invention mayalso adopt a configuration in which the same relative amount of cyclicshift is applied within codewords mapped to different space resources(layers) whereas different values of relative amount of cyclic shift areused among the codewords. When, for example, a case will be describedwhere when two codewords (codeword #0 and codeword #1) are mapped tofour space resources (layers #0 to #3), codeword #0 is mapped to layer#0 and layer #1 and codeword #1 is mapped to layer #2 and layer #3.Furthermore, suppose here, for example, that the amount of cyclicfrequency shift of layer #0 which serves as a reference is 8, therelative amount of cyclic frequency shift in layer #0 and layer #1 towhich codeword #0 is mapped is 5 and the relative amount of cyclicfrequency shift in layer #2 and layer #3 to which codeword #1 is mappedis 20. In this case, the amount of cyclic frequency shift of layer #0 is8, the amount of cyclic frequency shift of layer #1 (=amount of cyclicfrequency shift of layer #0+relative amount of cyclic frequency shift)is 8+5=13, the amount of cyclic frequency shift of layer #2 (=amount ofcyclic frequency shift of layer #1+relative amount of cyclic frequencyshift) is 13+20=33 and the amount of cyclic frequency shift of layer #3(=amount of cyclic frequency shift of layer #2+relative amount of cyclicfrequency shift) is 33+20=53. Thus, by reporting a relative amount ofcyclic frequency shift, it is possible to suppress overhead of controlinformation on the amount of cyclic frequency shift, maintain the samecommunication quality within codewords and flexibly set the amount ofcyclic frequency shift appropriate for codeword-specific communicationquality among codewords.

When the terminal maps one codeword to a plurality of space resources(layers) as shown in, for example, FIG. 22, the present invention mayuse repetition signals for signals mapped to a plurality of layers. Forexample, in FIG. 22, the terminal may map a copy (repetition signal) ofDFT output of codeword #0 (or codeword #1) mapped to layer #0 (or layer#2) to layer #0 and layer #1 (or layer #2 and layer #3).

Embodiment 7

A case has been described in Embodiment 6 where the terminal performs anindividual cyclic frequency shift on each space resource (layer) inone-dimensional domain only in the frequency domain. By contrast, thepresent embodiment is different from Embodiment 6 in that the terminalperforms a cyclic shift in a space domain in addition to the cyclicshift in the frequency domain and thereby performs a cyclic (space andfrequency) shift in a two-dimensional domain of space domain andfrequency domain.

To be more specific, the terminal according to the present embodimentapplies a cyclic frequency shift to a plurality of DFT outputs (aplurality of codewords) transmitted to the plurality of space resources(layers) for each space resource in the frequency domain as in the caseof Embodiment 6, and further applies a cyclic space (layer) shift toC-SC-FDMA signals (plurality of clusters) generated by dividing theplurality of DFT outputs (the plurality of codewords) transmittedthrough the plurality of space resources (layers) based on the unit ofpartially orthogonal bandwidths (e.g. clusters having partiallyorthogonal bandwidths) in the space domain (between space resources).

FIG. 23 shows a configuration of a transmitting apparatus (terminal)according to the present embodiment. In terminal 700 shown in FIG. 23,the same components as those in Embodiment 6 (FIG. 20) will be assignedthe same reference numerals and descriptions thereof will be omitted.Furthermore, terminal 700 shown in FIG. 23 is provided with two antennasthat transmit C-SC-FDMA signals using two space resources as in the caseof Embodiment 6. Furthermore, frequency shifting section 702 ofC-SC-FDMA processing section 701 shown in FIG. 23 performs the sameprocessing as that of shifting section 301 of C-SC-FDMA processingsection 601 in terminal 600 (FIG. 20) of Embodiment 6. Thus, terminal700 shown in FIG. 23 is different from terminal 600 (FIG. 20) ofEmbodiment 6 in that space shifting section 703 is provided betweendivision section 111 and precoding section 202.

In terminal 700 shown in FIG. 23, space shifting section 703 receivesinformation on an amount of shift (hereinafter referred to as “amount ofcyclic space shift”) in the space resource region (layer) for eachpartially orthogonal bandwidth (e.g. cluster having a partiallyorthogonal bandwidth) from control section 106 as input. Furthermore,space shifting section 703 receives C-SC-FDMA signals (a plurality ofclusters) subjected to individual cyclic frequency shift for eachcodeword (or each layer) from each division section 111 of C-SC-FDMAprocessing section 701 as input as in the case of Embodiment 6. Spaceshifting section 703 then applies a cyclic space shift to each clusterbetween space resources (layers) according to an individual amount ofcyclic space shift for each partially orthogonal bandwidth (cluster). Tobe more specific, space shifting section 703 applies a cyclic spaceshift to C-SC-FDMA signals (a plurality of clusters) generated bydividing codewords (SC-FDMA signals) transmitted through a plurality ofspace resources (layers) in units of orthogonal bandwidth. Spaceshifting section 703 then outputs the clusters after the cyclic spaceshift to precoding section 202.

Next, details of the cyclic space shifting processing by space shiftingsection 703 of terminal 700 will be described.

A case will be described below where terminal 700 maps two codewords(codeword #0 and codeword #1) to two different space resources (here,layers) as in the case of Embodiment 6. Furthermore, C-SC-FDMAprocessing sections 701-1 and 701-2 of terminal 700 apply a cyclicfrequency shift to codeword #1 and codeword #2 (FIG. 21B) shown in FIG.21A as in the case of Embodiment 6, divide the SC-FDMA signal after thecyclic frequency shift with partially orthogonal bandwidths and generatetwo cluster of cluster #0 and cluster #1 (FIG. 21C). That is, terminal700 performs cyclic shifting in one-dimensional domain of the frequencydomain through the processing shown in FIG. 21B.

As shown in FIG. 24, space shifting section 703 then applies a cyclicspace shift to each cluster (cluster #0 and cluster #1) after the cyclicfrequency shift between space resources (layers) in units of partiallyorthogonal bandwidth, that is, for each cluster having a partiallyorthogonal bandwidth. In FIG. 24, an amount of cyclic space shift forcluster #0=0 (without cyclic space shift) and an amount of cyclic spaceshift for cluster #0=1 (with cyclic space shift). Thus, as shown in FIG.24, space shifting section 703 applies a cyclic space shift to cluster#0 with an amount of cyclic space shift=0 (without cyclic space shift)in units of partially orthogonal bandwidth N′=12. Likewise, as shown inFIG. 24, space shifting section 703 applies a cyclic space shift tocluster #1 with an amount of cyclic space shift=1 in units of partiallyorthogonal bandwidth N′=60. As shown in FIG. 24, in cluster #1, a signalof codeword #0 is mapped to layer #1 and a signal of codeword #1 ismapped to layer #0. That is, terminal 700 performs a cyclic shift inone-dimensional domain of the space domain through the processing shownin FIG. 24.

By this means, according to the present embodiment, the terminal appliesa cyclic space shift in units of partially orthogonal bandwidth inaddition to the processing in Embodiment 6, and can thereby furtherimprove the frequency diversity effect and space diversity effect whilemaintaining a partially orthogonal relationship between column vectorsin the frequency domain.

A case has been described in the present embodiment where in terminal700 shown in FIG. 23, frequency shifting section 702 applies a cyclicfrequency shift to a frequency domain signal and space shifting section703 then applies a cyclic space shift in the space domain. However, inthe present invention, the order of processing of cyclic frequency shiftand cyclic space shift in the terminal may be reversed. That is, theterminal according to the present invention may apply a cyclic space(layer) shift in the space domain to a signal and then apply a cyclicfrequency shift in the frequency domain.

Furthermore, in the present invention, the terminal may perform only acyclic space (layer) shift on a signal in one-dimensional domain of thespace domain without performing any cyclic frequency shift in thefrequency domain. That is, the terminal may apply a cyclic space (layer)shift to C-SC-FDMA signals (plurality of clusters) generated by dividingan SC-FDMA signal transmitted through a plurality of space resources inunits of partially orthogonal bandwidths. This corresponds to a casewhere all amounts of cyclic frequency shift in each space resource(layer) are set to 0 in the present embodiment that performs cyclicshifting in the two-dimensional domain of the frequency domain and spacedomain. Alternatively, this corresponds to the configuration oftransmitting apparatus (terminal 700) in FIG. 23 adapted such thatfrequency shifting section 702 is omitted and the DFT output (SC-FDMAsignal) outputted from DFT section 110 is directly inputted to divisionsection 111 without being subjected to any cyclic frequency shift. Thatis, the terminal may apply a cyclic space (layer) shift to the DFToutput of each space resource (layer) to which no cyclic frequency shiftin the frequency domain is applied, only in the space domain (betweenspace resources) based on the unit of partially orthogonal bandwidths(e.g. clusters having partially orthogonal bandwidths). This makes itpossible to improve space diversity effects while maintaining apartially orthogonal relationship within clusters in the frequencydomain.

Furthermore, a case has been described in FIG. 24 of the presentembodiment where the terminal performs cyclic space shifting on aplurality of clusters between space resources for each cluster having alength of partially orthogonal bandwidth. However, in the presentinvention, as shown in FIG. 25, the terminal may also apply a cyclicspace (layer) shift to a plurality of clusters between space resourcesin units of bandwidths (lengths) partially orthogonal to each other in ashorter length than the cluster size (narrower bandwidth than thecluster bandwidth). In FIG. 25, the terminal applies different cyclicspace (layer) shifts (amount of cyclic space shift=1 and 2) in the spacedomain every two partially orthogonal bandwidths (N′=12 and N′=48) incluster #1 (N′=60). This makes it possible to increase apparent channelrandomness in the cluster through a cyclic space shift while maintaininga partially orthogonal relationship between column vectors in thefrequency domain and thereby further improve space diversity.

Furthermore, a case has been described in the present embodiment wherethe partially orthogonal bandwidth is used as the unit of the frequencydomain to which a cyclic space (layer) shift is applied. However, thepresent invention may also use a multiple of a minimum partiallyorthogonal bandwidth of a plurality of cluster bandwidths as the unit ofthe frequency domain to which a cyclic space (layer) shift is applied.When, for example, the minimum partially orthogonal bandwidth is assumedto be B_(min), the unit of the frequency domain to which a cyclic spaceshift is applied may be defined as kB_(min) (k is an integer). The basestation may determine the amount of cyclic space shift in units ofkB_(min), and report the determined amount of cyclic space shift to theterminal. By this means, by only performing simple control using aplurality of cluster bandwidths, it is possible to define the unit ofthe frequency domain to which a cyclic space (layer) shift is appliedand also obtain effects similar to those of the present embodiment.

Furthermore, in the present invention, amount of cyclic space shift y inthe unit of frequency domain (e.g. cluster unit having a partiallyorthogonal bandwidth) to which a cyclic space (layer) shift is appliedmay differ from one unit of frequency domain to which a cyclic space(layer) shift is applied to another. Moreover, the rotating direction ofa cyclic space (layer) shift may be one of plus (+) and minus (−). Thatis, the amount of cyclic space shift may be one of +y and −y.

Furthermore, in the present invention, two amounts of shift (z and y)may be set by associating amount of cyclic frequency shift z with amountof cyclic space shift y. For example, amount of cyclic frequency shiftz_(i) of layer #i may be represented by a function of amount of cyclicspace shift y_(i) of cluster #i, or conversely, amount of cyclic spaceshift y_(i) of cluster #i may be represented by a function of amount ofcyclic frequency shift z_(i) of layer #i. For example, such a definitionmay be possible; amount of cyclic space shift z_(i)=(amount of cyclicfrequency shift y_(i)) mod (number of layers). Here “mod” represents amodulo operation. The receiving apparatus may report only amount ofcyclic frequency shift y_(i) to the transmitting apparatus and thetransmitting apparatus may identify amount of cyclic space shift z_(i)according to the above described function. This makes it possible toreduce the amount of information required to report two amounts ofcyclic shift in the space domain and the frequency domain and at thesame time improve the space diversity effect and the frequency diversityeffect.

Furthermore, in the present invention, when identification information(flag) indicating whether or not to apply a cyclic space shift oridentification information (flag) indicating whether or not to apply acyclic frequency shift is reported from the receiving apparatus (basestation) to the transmitting apparatus (terminal), the two pieces ofidentification information (flags) may be shared and one piece of thetwo-dimensional information indicating whether or not to apply a cyclicspace shift and a frequency shift may be reported from the receivingapparatus to the transmitting apparatus. This makes it possible toreduce the amount of control information on the identificationinformation and at the same time obtain a space diversity effect and afrequency diversity effect.

Furthermore, the present embodiment has described in FIG. 24 and FIG.25, when two clusters (cluster #0 and cluster #1) are mapped tonon-continuous frequency bands, the method for the terminal to perform acyclic shift (two-dimensional shift) in two-dimensional domain of thefrequency domain and space domain or the method for the terminal toperform a cyclic shift (one-dimensional shift) in one-dimensional domainof the space domain. However, the present invention may also beapplicable to a case where a plurality of clusters are mapped tocontinuous frequency bands. When, for example, performing atwo-dimensional shift in the frequency domain and space domain, theterminal cyclically frequency-shifts a plurality of DFT outputs in thefrequency domain respectively, and then cyclically space (layer)-shiftsthe DFT output of each cyclically frequency-shifted space resource(layer) in the space domain (between space resources) based on the unitof the partially orthogonal bandwidths (e.g. clusters having partiallyorthogonal bandwidths) described in Embodiment 1 and Embodiment 4. Theterminal may then map the signals cyclically shifted in the frequencydomain and space domain to continuous frequency bands of each spaceresource (layer). Furthermore, when, for example, performingone-dimensional shifting in the space domain, the terminal cyclicallyspace (layer)-shifts the plurality of DFT outputs based on the unit ofthe partially orthogonal bandwidths (e.g. clusters having partiallyorthogonal bandwidths) described in Embodiment 1 and Embodiment 4. Afterthat, the cyclically space-shifted signals may be mapped to continuousfrequency bands of the respective space resources (layers).

Embodiment 8

A case has been described in Embodiment 5 where the terminal applies anindividual cyclic frequency shift to the DFT output (SC-FDMA signal) foreach space resource (layer). By contrast, in the present embodiment, theterminal applies an individual cyclic frequency shift to the DFT output(SC-FDMA signal) within a DFT band in different time domains (for eachdifferent time resource). The terminal then divides cyclicallyfrequency-shifted signal with a partially orthogonal bandwidth andthereby generates a plurality of clusters.

To be more specific, the terminal according to the present embodimentchanges amount of cyclic frequency shift z_(i) of a C-SC-FDMA signaltransmitted at each time i in a DFT band (DFT size N=72 points in FIG.26) as time advances while maintaining mapping positions in thefrequency domain (frequency bands) of two clusters (cluster #0 andcluster #1) as shown in FIG. 26. For example, as shown in FIG. 26,amount of cyclic frequency shift z₀=0 at time #0, amount of cyclicfrequency shift z₁=12 at time #1, amount of cyclic frequency shift z₂=36at time #2 and amount of cyclic frequency shift z₃=60 at time #3. Thatis, the terminal applies a cyclic frequency shift to the DFT output(SC-FDMA signal) in different time domains (every different timeresource) using different amounts of cyclic frequency shift in the DFTband (72 points). As shown in FIG. 26, the terminal then divides the DFToutput after the cyclic frequency shift with a partially orthogonalbandwidth and generates two clusters: cluster #0 and cluster #1.

Thus, the present embodiment can improve the time diversity effect andfrequency diversity effect while maintaining partial orthogonalitybetween column vectors of the DFT matrix within clusters withoutchanging frequency bands to which the DFT output (SC-FDMA signal) isallocated (while maintaining mapping positions (frequency band) in thefrequency domain).

The amount of cyclic frequency shift may be changed using a symbol unit,slot unit, subframe unit, frame unit or retransmission unit or the likeas the time unit.

The embodiments of the present invention have been described so far.

A case has been described in the above embodiments using the term of“column vector of a DFT matrix” where the terminal divides DFT output(an SC-FDMA signal) in a length (bandwidth) which is partiallyorthogonal among column vectors and generates a plurality of clusters(C-SC-FDMA signals). Here, the DFT matrix is a symmetric matrix. Forexample, each element of an n-th column vector of an N×N DFT matrix isidentical to each element of an n-th row vector. Thus, in the presentinvention, even when using a matrix transposed from a DFT matrix as aprecoding matrix, the terminal may divide a precoded signal with alength (bandwidth) partially orthogonal among row vectors of the DFTmatrix. That is, the SC-FDMA signal division method described in theabove embodiments may be applied to a signal precoded by a transposematrix of the DFT matrix. Thus, even when using such a matrix transposedfrom the DFT matrix as a precoding matrix, effects similar to those inthe above embodiments can be obtained.

Furthermore, the present invention may also use a complex conjugatematrix of the DFT matrix or a complex conjugate transpose matrix of theDFT matrix (Hermitian transpose matrix of the DFT matrix) as theprecoding matrix. Here, the complex conjugate matrix of the DFT matrixand the complex conjugate transpose matrix of the DFT matrix (Hermitiantranspose matrix of the DFT matrix) are symmetric matrixes. Therefore,each element of an n-th column vector of a complex conjugate matrix ofan N×N DFT matrix (or complex conjugate transpose matrix (Hermitiantranspose matrix of the DFT matrix)) is identical to each element of ann-th row vector. Thus, partially orthogonal conditions of equation 1 andequation 2 can be applied to the complex conjugate transpose matrix ofthe DFT matrix (Hermitian transpose matrix of the DFT matrix), andtherefore the terminal may divide a precoded signal with the partiallyorthogonal length (bandwidth) described in the above embodiments. Thatis, the SC-FDMA signal division method described in the aboveembodiments may be applied to the signal precoded by the complexconjugate matrix of the DFT matrix or the complex conjugate transposematrix of the DFT matrix (Hermitian transpose matrix of the DFT matrix).This makes it possible to obtain effects similar to those in the aboveembodiments even when using the complex conjugate matrix of the DFTmatrix or complex conjugate transpose matrix of the DFT matrix(Hermitian transpose matrix of the DFT matrix) as the precoding matrix.

Furthermore, the present invention may also use an inverse matrix of theDFT matrix as the precoding matrix. The inverse matrix of the DFT matrixis equivalent to the complex conjugate transpose matrix of the DFTmatrix (Hermitian transpose matrix of the DFT matrix). Therefore, whenusing the inverse matrix of the DFT matrix as the precoding matrix, theSC-FDMA signal division method described in the above embodiments may beapplied to a signal precoded by the inverse matrix of the DFT matrix.This makes it possible to obtain effects similar to those in the aboveembodiments even when using the inverse matrix of the DFT matrix as theprecoding matrix.

A terminal configuration (e.g. FIG. 9 and FIG. 20) has been shown inabove Embodiments 2 and 6 in which the DFT section→divisionsection→precoding section are connected in that order. However, thepresent invention may also adopt a terminal configuration in which theDFT section→precoding section→division section are connected in thatorder. In this case, the terminal transforms respective transmissionsymbol sequences in which pilot signals are multiplexed from the timedomain to frequency domain signals through DFT processing by the DFTsection and then performs linear precoding on each subcarrier frequencydomain signal through the precoding section (e.g. multiplying two DFToutput signals in a certain subcarrier by a precoding matrix expressedin matrix form). The terminal may then perform division processing onthe SC-FDMA signal for the precoded frequency-domain signal component bythe division section using one of the division methods of the aboveembodiments.

Furthermore, a case has been described in the above embodiments where anSC-FDMA signal is divided with a partially orthogonal bandwidth in thefrequency domain. However, the present invention may also be applied toMIMO transmission in which a signal is spread in the time domain throughdirect sequence code division multiple access (DS-CDMA) or the likeusing a DFT matrix (transpose matrix of DFT matrix, complex conjugatematrix of DFT matrix, complex conjugate transpose matrix of the DFTmatrix or inverse matrix of DFT matrix) and the spread signals arecode-multiplexed in the space domain. In this case, a signal obtainedthrough the spreading of the DFT matrix (transpose matrix of the DFTmatrix, complex conjugate matrix of the DFT matrix, complex conjugatetranspose matrix of the DFT matrix or inverse matrix of the DFT matrix)in the time domain and code multiplexing in the space domain may bedivided with a partially orthogonal bandwidth as in the case of theabove embodiments and the respective divided signals may be mapped todiscontinuous time resources or space resources. Thus, it is possible toobtain effects similar to those in the above embodiments.

Furthermore, above Embodiments 1 to 8 may also be used in combinationwith each other.

Furthermore, a case has been described in the above embodiments wherethe radio communication apparatus according to the present invention isprovided for terminal 100 (FIG. 1), terminal 200 (FIG. 9), terminal 300(FIG. 15), terminal 500 (FIG. 19), terminal 600 (FIG. 20) or terminal700 (FIG. 23), but the radio communication apparatus according to thepresent invention may also be provided for the base station.

Furthermore, the terminal may also be referred to as UE (User Equipment:UE) and the base station may also be referred to as Node B or BS (BaseStation).

Furthermore, the present invention has been described as an antenna inthe above embodiments, but the present invention is likewise applicableto an antenna port.

The antenna port refers to a logical antenna made up of one or aplurality of physical antennas. That is, the antenna port does notalways refer to one physical antenna but may refer to an array antennamade up of a plurality of antennas or the like.

For example, 3GPP LTE does not define of how many physical antennas anantenna port is made up, but defines the antenna port as a minimum unitthat the base station can transmit different reference signals.

Furthermore, the antenna port may also be defined as a minimum unit formultiplying a precoding vector weight.

Moreover, although cases have been described with the embodiments abovewhere the present invention is configured by hardware, the presentinvention may be implemented by software.

Each function block employed in the description of the aforementionedembodiments may typically be implemented as an LSI constituted by anintegrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells within an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosures of Japanese Patent Application No. 2008-242716, filed onSep. 22, 2008, and Japanese Patent Application No. 2009-201740, filed onSep. 1, 2009, including the specifications, drawings and abstracts areincorporated herein by reference in their entirety.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a mobile communication system orthe like.

1. A communication apparatus comprising: a receiver which, in operation,receives signals mapped on a plurality of frequency bands in a frequencydomain, each frequency band including a plurality of subcarriers, eachfrequency band being located at a position separate from position(s) ofother(s) of the plurality of frequency bands, and a size of at least oneof the plurality of frequency bands being a multiple of a product of twoor more powers of prime numbers, the prime numbers being integer numbersthat are greater than 1 and are different from each other, an exponentfor at least one of the prime numbers being an integer greater than 1; acombiner which, in operation, combines the received signals into acombined signal; and a transformer which, in operation, transforms thecombined signal in the frequency domain into a symbol sequence in a timedomain with an inverse discrete Fourier transform (IDFT) having a sizethat is a product of powers of a plurality of values, the plurality ofvalues being integer numbers that are greater than 1 and are differentfrom each other, an exponent for at least one of the plurality of valuesbeing an integer greater than
 1. 2. The communication apparatusaccording to claim 1, wherein a number of the plurality of frequencybands is two, and a size of one of the two frequency bands is a multipleof a product of two or more powers of prime numbers.
 3. Thecommunication apparatus according to claim 1, wherein the prime numbersare selected in order from a smaller prime number.
 4. The communicationapparatus according to claim 1, wherein a size of all of the pluralityof frequency bands is a multiple of a product of two or more powers ofprime numbers.
 5. The communication apparatus according to claim 1,wherein a first exponent for a first prime number is equal to or greaterthan a second exponent for a second prime number that is greater thanthe first prime number.
 6. The communication apparatus according toclaim 1, wherein a size of each of the plurality of frequency bands isone minimum division unit or multiple minimum division units, and theminimum division unit being a product of two or more powers of primenumbers, and wherein a first exponent for a first prime number is equalto or greater than a second exponent for a second prime number that isgreater than the first prime number.
 7. The communication apparatusaccording to claim 6, wherein a size of all of the plurality offrequency bands is a multiple of the minimum division unit.
 8. Thecommunication apparatus according to claim 7, further comprising: atransmitter which, in operation, transmits allocation informationindicating a frequency position of each of the plurality of frequencybands, the frequency position being indicated in terms of the minimumdivision unit.
 9. The communication apparatus according to claim 1,further comprising: a transmitter which, in operation, transmitsallocation information including the size of at least one of theplurality of frequency bands.
 10. A communication method performed by acommunication apparatus comprising: receiving signals mapped on aplurality of frequency bands in a frequency domain, each frequency bandincluding a plurality of subcarriers, each frequency band being locatedat a position separate from position(s) of other(s) of the plurality offrequency bands, and a size of at least one of the plurality offrequency bands being a multiple of a product of two or more powers ofprime numbers, the prime numbers being integer numbers that are greaterthan 1 and are different from each other, an exponent for at least oneof the prime numbers being an integer greater than 1; combining thereceived signals into a combined signal; and transforming the combinedsignal in the frequency domain into a symbol sequence in a time domainwith an inverse discrete Fourier transform (IDFT) having a size that isa product of powers of a plurality of values, the plurality of valuesbeing integer numbers that are greater than 1 and are different fromeach other, an exponent for at least one of the plurality of valuesbeing an integer greater than
 1. 11. The communication method accordingto claim 10, wherein a number of the plurality of frequency bands istwo, and a size of one of the two frequency bands is a multiple of aproduct of two or more powers of prime numbers.
 12. The communicationmethod according to claim 10, wherein the prime numbers are selected inorder from a smaller prime number.
 13. The communication methodaccording to claim 10, wherein a size of all of the plurality offrequency bands is a multiple of a product of two or more powers ofprime numbers.
 14. The communication method according to claim 10,wherein a first exponent for a first prime number is equal to or greaterthan a second exponent for a second prime number that is greater thanthe first prime number.
 15. The communication method according to claim10, wherein a size of each of the plurality of frequency bands is oneminimum division unit or multiple minimum division units, and theminimum division unit being a product of two or more powers of primenumbers, and wherein a first exponent for a first prime number is equalto or greater than a second exponent for a second prime number that isgreater than the first prime number.
 16. The communication methodaccording to claim 15, wherein a size of all of the plurality offrequency bands is a multiple of the minimum division unit.
 17. Thecommunication method according to claim 16, further comprising:transmitting allocation information indicating a frequency position ofeach of the plurality of frequency bands, the frequency position beingindicated in terms of the minimum division unit.
 18. The communicationmethod according to claim 10, further comprising: transmittingallocation information including the size of at least one of theplurality of frequency bands.